Add staticcheck to github actions

Remove TODOs that were already taken care of (#10454 )
Forkchoice spec test: set boost with deterministic timing (#10428 )
2026-01-10 05:47:59 -05:00 · 2022-03-30 09:55:19 -05:00 · 2022-03-30 13:24:02 +00:00 · 2022-03-29 19:48:33 +00:00 · 2022-03-29 06:55:41 -07:00 · 2022-03-28 22:17:31 +00:00
1715 changed files with 102918 additions and 38287 deletions
--- a/.bazelrc
+++ b/.bazelrc
@@ -36,6 +36,9 @@ run --define blst_disabled=false
 build:blst_disabled --define blst_disabled=true
 build:blst_disabled --define gotags=blst_disabled

+build:minimal --//proto:network=minimal
+build:minimal --@io_bazel_rules_go//go/config:tags=minimal
+
 # Release flags
 build:release --compilation_mode=opt
 build:release --config=llvm
@@ -59,20 +62,7 @@ build:llvm-asan --config=llvm
 build:llvm-asan --config=asan
 build:llvm-asan --linkopt -fuse-ld=ld.lld

-build:fuzz --define=gotags=libfuzzer
-build:fuzz --config=llvm-asan
-build:fuzz --copt=-fsanitize=fuzzer-no-link
-build:fuzz --linkopt=-fsanitize=fuzzer
-build:fuzz --copt=-fno-omit-frame-pointer
-build:fuzz --define=FUZZING_ENGINE=libfuzzer
-build:fuzz --copt=-DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
-build:fuzz --linkopt -Wl,--no-as-needed
-build:fuzz --define=gc_goopts=-d=libfuzzer,checkptr
-build:fuzz --run_under=//tools:fuzz_wrapper
-build:fuzz --compilation_mode=opt
-build:fuzz --define=blst_disabled=true
-
-test:fuzz --local_test_jobs="HOST_CPUS*.5"
+build:fuzz --@io_bazel_rules_go//go/config:tags=fuzz

 # Build binary with cgo symbolizer for debugging / profiling.
 build:cgo_symbolizer --config=llvm
@@ -227,3 +217,6 @@ build:remote --remote_local_fallback

 # Ignore GoStdLib with remote caching
 build --modify_execution_info='GoStdlib.*=+no-remote-cache'
+
+# Set bazel gotag
+build --define gotags=bazel
--- a/.bazelversion
+++ b/.bazelversion
@@ -1 +1 @@
-3.7.0
+5.0.0
--- a/.buildkite-bazelrc
+++ b/.buildkite-bazelrc
@@ -10,40 +10,37 @@

 # Prysm specific remote-cache properties.
 #build:remote-cache --disk_cache=
-build:remote-cache --remote_download_toplevel
+build:remote-cache --remote_download_minimal
 build:remote-cache --remote_cache=grpc://bazel-remote-cache:9092
 build:remote-cache --experimental_remote_downloader=grpc://bazel-remote-cache:9092
 build:remote-cache --remote_local_fallback
+build:remote-cache --experimental_remote_cache_async
+build:remote-cache --experimental_remote_merkle_tree_cache
+build:remote-cache --experimental_action_cache_store_output_metadata
+build:remote-cache --experimental_remote_cache_compression
 # Enforce stricter environment rules, which eliminates some non-hermetic
 # behavior and therefore improves both the remote cache hit rate and the
 # correctness and repeatability of the build.
 build:remote-cache --incompatible_strict_action_env=true

+build --experimental_use_hermetic_linux_sandbox
+
 # Import workspace options.
 import %workspace%/.bazelrc

-startup --host_jvm_args=-Xmx2g --host_jvm_args=-Xms2g
-query --repository_cache=/tmp/repositorycache
-query --experimental_repository_cache_hardlinks
-build --repository_cache=/tmp/repositorycache
-build --experimental_repository_cache_hardlinks
+startup --host_jvm_args=-Xmx4g --host_jvm_args=-Xms2g
 build --experimental_strict_action_env
-build --disk_cache=/tmp/bazelbuilds
-build --experimental_multi_threaded_digest
 build --sandbox_tmpfs_path=/tmp
 build --verbose_failures
 build --announce_rc
 build --show_progress_rate_limit=5
-build --curses=yes --color=no
+build --curses=no --color=no
 build --keep_going
 build --test_output=errors
 build --flaky_test_attempts=5
 # Disabled race detection due to unstable test results under constrained environment build kite
 # build --features=race

-# Disable flaky test detection for fuzzing.
-test:fuzz --flaky_test_attempts=1
-
 # Better caching
 build:nostamp --nostamp
 build:nostamp --workspace_status_command=./hack/workspace_status_ci.sh
--- a/.github/CODEOWNERS
+++ b/.github/CODEOWNERS
@@ -6,3 +6,11 @@

 # Anyone on prylabs team can approve dependency updates.
 deps.bzl @prysmaticlabs/core-team
+
+# Radek and Nishant are responsible for changes that can affect the native state feature.
+# See https://www.notion.so/prysmaticlabs/Native-Beacon-State-Redesign-6cc9744b4ec1439bb34fa829b36a35c1
+/beacon-chain/state/fieldtrie/ @rkapka @nisdas
+/beacon-chain/state/v1/ @rkapka @nisdas
+/beacon-chain/state/v2/ @rkapka @nisdas
+/beacon-chain/state/v3/ @rkapka @nisdas
+/beacon-chain/state/state-native/ @rkapka @nisdas
--- a/.github/actions/gomodtidy/entrypoint.sh
+++ b/.github/actions/gomodtidy/entrypoint.sh
@@ -7,7 +7,7 @@ cd $GITHUB_WORKSPACE
 cp go.mod go.mod.orig
 cp go.sum go.sum.orig

-go mod tidy
+go mod tidy -compat=1.17

 echo "Checking go.mod and go.sum:"
 checks=0
--- a/.github/workflows/go.yml
+++ b/.github/workflows/go.yml
@@ -34,12 +34,17 @@ jobs:
      - name: Gosec security scanner
        uses: securego/gosec@master
        with:
-          args: '-exclude-dir=crypto/bls/herumi ./...'
+          args: '-exclude=G307 -exclude-dir=crypto/bls/herumi ./...'

      - name: Golangci-lint
        uses: golangci/golangci-lint-action@v2
        with:
-          args: --print-issued-lines --sort-results --no-config --timeout=10m --disable-all -E deadcode --skip-files=validator/web/site_data.go
+          args: --print-issued-lines --sort-results --no-config --timeout=10m --disable-all -E deadcode  -E errcheck -E gosimple --skip-files=validator/web/site_data.go --skip-dirs=proto
+      
+      - name: staticcheck
+        uses: dominikh/staticcheck-action@v1.1.0
+        with:
+          version: "2021.1.1"

  build:
    name: Build
--- a/.gitignore
+++ b/.gitignore
@@ -30,9 +30,5 @@ password.txt
 # Dist files
 dist

-# libfuzzer
-oom-*
-crash-*
-
 # deepsource cli
 bin
--- a/.well-known/security.txt
+++ b/.well-known/security.txt
@@ -5,21 +5,22 @@ Contact: mailto:security@prysmaticlabs.com
 Encryption: openpgp4fpr:0AE0051D647BA3C1A917AF4072E33E4DF1A5036E
 Encryption: openpgp4fpr:CD08DE68C60B82D3EE2A3F7D95452A701810FEDB
 Encryption: openpgp4fpr:317D6E91058F8F3C2303BA7756313E44581297A6
+Encryption: openpgp4fpr:79C59A585E3FD3AFFA00F5C22940A6479DA7C9EC
 Preferred-Languages: en
 Canonical: https://github.com/prysmaticlabs/prysm/tree/master/.well-known/security.txt
 -----BEGIN PGP SIGNATURE-----

-iQIzBAEBCgAdFiEECuAFHWR7o8GpF69AcuM+TfGlA24FAl++klgACgkQcuM+TfGl
-A27rQw/6A29p1W20J0v+h218p8XWLSUpTIGLnZTxw6KqdyVXMzlsQK0YG4G2s2AB
-0LKh7Ae/Di5E0U+Z4AjUW5nc5eaCxK36GMscH9Ah0rgJwNYxEJw7/2o8ZqVT/Ip2
-+56rFihRqxFZfaCNKFVuZFaL9jKewV9FKYP38ID6/SnTcrOHiu2AoAlyZGmB03p+
-iT57SPRHatygeY4xb/gwcfREFWEv+VHGyBTv8A+6ABZDxyurboCFMERHzFICrbmk
-8UdHxxlWZDnHAbAUyAwpERC5znx6IHXQJwF8TMtu6XY6a6axT2XBOyJDF9/mZOz+
-kdkz6loX5uxaQBGLtTv6Kqf1yUGANOZ16VhHvWwL209LmHmigIVQ+qSM6c79PsW/
-vrsqdz3GBsiMC5Fq2vYgnbgzpfE8Atjn0y7E+j4R7IvwOAE/Ro/b++nqnc4YqhME
-P/yTcfGftaCrdSNnQCXeoV9JxpFM5Xy8KV3eexvNKbcgA/9DtgxL5i+s5ZJkUT9A
-+qJvoRrRyIym32ghkHgtFJKB3PLCdobeoOVRk6EnMo9zKSiSK2rZEJW8Ccbo515D
-W9qUOn3GF7lNVuUFAU/YKEdmDp/AVaViZ7vH+8aq0LC0HBkZ8XlzWnWoArS8sMhw
-fX0R9g/HMgrwNte/d0mwim5lJ2Plgv60Bh4grJqwZJeWbU0zi1U=
-=uW+X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+=V7L0
 -----END PGP SIGNATURE-----
--- a/BUILD.bazel
+++ b/BUILD.bazel
@@ -3,7 +3,7 @@ load("@com_github_atlassian_bazel_tools//gometalinter:def.bzl", "gometalinter")
 load("@com_github_atlassian_bazel_tools//goimports:def.bzl", "goimports")
 load("@io_kubernetes_build//defs:run_in_workspace.bzl", "workspace_binary")
 load("@io_bazel_rules_go//go:def.bzl", "nogo")
-load("@graknlabs_bazel_distribution//common:rules.bzl", "assemble_targz", "assemble_versioned")
+load("@vaticle_bazel_distribution//common:rules.bzl", "assemble_targz", "assemble_versioned")
 load("@bazel_skylib//rules:common_settings.bzl", "string_setting")

 prefix = "github.com/prysmaticlabs/prysm"
@@ -16,6 +16,8 @@ exports_files([
 # gazelle:map_kind go_library go_library @prysm//tools/go:def.bzl
 # gazelle:map_kind go_test go_test @prysm//tools/go:def.bzl
 # gazelle:map_kind go_repository go_repository @prysm//tools/go:def.bzl
+# gazelle:build_tags bazel
+# gazelle:exclude tools/analyzers/**/testdata/**
 gazelle(
    name = "gazelle",
    prefix = prefix,
@@ -86,50 +88,52 @@ nogo(
    config = "nogo_config.json",
    visibility = ["//visibility:public"],
    deps = [
-        "@org_golang_x_tools//go/analysis/passes/unsafeptr:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/unreachable:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/unmarshal:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/tests:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/structtag:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/stdmethods:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/shift:go_tool_library",
-        # "@org_golang_x_tools//go/analysis/passes/shadow:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/printf:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/pkgfact:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/nilness:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/nilfunc:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/loopclosure:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/httpresponse:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/findcall:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/deepequalerrors:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/ctrlflow:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/copylock:go_tool_library",
-        #  "@org_golang_x_tools//go/analysis/passes/cgocall:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/buildtag:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/buildssa:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/bools:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/atomicalign:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/atomic:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/assign:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/inspect:go_tool_library",
-        "@org_golang_x_tools//go/analysis/passes/asmdecl:go_tool_library",
-        "//tools/analyzers/maligned:go_tool_library",
-        "//tools/analyzers/cryptorand:go_tool_library",
-        "//tools/analyzers/errcheck:go_tool_library",
-        "//tools/analyzers/featureconfig:go_tool_library",
-        "//tools/analyzers/comparesame:go_tool_library",
-        "//tools/analyzers/shadowpredecl:go_tool_library",
-        "//tools/analyzers/nop:go_tool_library",
-        "//tools/analyzers/slicedirect:go_tool_library",
-        "//tools/analyzers/interfacechecker:go_tool_library",
-        "//tools/analyzers/ineffassign:go_tool_library",
-        "//tools/analyzers/properpermissions:go_tool_library",
+        "@org_golang_x_tools//go/analysis/passes/unsafeptr:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/unreachable:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/unmarshal:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/tests:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/structtag:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/stdmethods:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/shift:go_default_library",
+        # "@org_golang_x_tools//go/analysis/passes/shadow:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/printf:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/pkgfact:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/nilness:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/nilfunc:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/loopclosure:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/httpresponse:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/findcall:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/deepequalerrors:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/ctrlflow:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/copylock:go_default_library",
+        #  "@org_golang_x_tools//go/analysis/passes/cgocall:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/buildtag:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/buildssa:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/bools:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/atomicalign:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/atomic:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/assign:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/inspect:go_default_library",
+        "@org_golang_x_tools//go/analysis/passes/asmdecl:go_default_library",
+        "//tools/analyzers/maligned:go_default_library",
+        "//tools/analyzers/cryptorand:go_default_library",
+        "//tools/analyzers/errcheck:go_default_library",
+        "//tools/analyzers/featureconfig:go_default_library",
+        "//tools/analyzers/comparesame:go_default_library",
+        "//tools/analyzers/shadowpredecl:go_default_library",
+        "//tools/analyzers/nop:go_default_library",
+        "//tools/analyzers/slicedirect:go_default_library",
+        "//tools/analyzers/interfacechecker:go_default_library",
+        "//tools/analyzers/ineffassign:go_default_library",
+        "//tools/analyzers/properpermissions:go_default_library",
+        "//tools/analyzers/recursivelock:go_default_library",
+        "//tools/analyzers/uintcast:go_default_library",
    ] + select({
        # nogo checks that fail with coverage enabled.
        ":coverage_enabled": [],
        "//conditions:default": [
-            "@org_golang_x_tools//go/analysis/passes/lostcancel:go_tool_library",
-            "@org_golang_x_tools//go/analysis/passes/composite:go_tool_library",
+            "@org_golang_x_tools//go/analysis/passes/lostcancel:go_default_library",
+            "@org_golang_x_tools//go/analysis/passes/composite:go_default_library",
        ],
    }),
 )
@@ -144,21 +148,6 @@ common_files = {
    "//:README.md": "README.md",
 }

-toolchain(
-    name = "built_cmake_toolchain",
-    toolchain = "@rules_foreign_cc//tools/build_defs/native_tools:built_cmake",
-    toolchain_type = "@rules_foreign_cc//tools/build_defs:cmake_toolchain",
-)
-
-string_setting(
-    name = "gotags",
-    build_setting_default = "",
-    values = [
-        "",
-        "libfuzzer",
-    ],
-)
-
 sh_binary(
    name = "prysm_sh",
    srcs = ["prysm.sh"],
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -190,7 +190,7 @@ Anyone can become a part-time contributor and help out on implementing Ethereum

 Core contributors are remote contractors of Prysmatic Labs, LLC. and are considered critical team members of our organization. Core devs have all of the responsibilities of part-time contributors plus the majority of the following:

-   Stay up to date on the latest beacon chain sepcification
+-   Stay up to date on the latest beacon chain specification
 -   Monitor github issues and PR’s to make sure owner, labels, descriptions are correct
 -   Formulate independent ideas, suggest new work to do, point out improvements to existing approaches
 -   Participate in code review, ensure code quality is excellent, and have ensure high code coverage
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@

 [![Build status](https://badge.buildkite.com/b555891daf3614bae4284dcf365b2340cefc0089839526f096.svg?branch=master)](https://buildkite.com/prysmatic-labs/prysm)
 [![Go Report Card](https://goreportcard.com/badge/github.com/prysmaticlabs/prysm)](https://goreportcard.com/report/github.com/prysmaticlabs/prysm)
-[![ETH2.0_Spec_Version 1.0.0](https://img.shields.io/badge/ETH2.0%20Spec%20Version-v1.0.0-blue.svg)](https://github.com/ethereum/consensus-specs/tree/v1.0.0)
+[![Consensus_Spec_Version 1.1.8](https://img.shields.io/badge/Consensus%20Spec%20Version-v1.1.8-blue.svg)](https://github.com/ethereum/consensus-specs/tree/v1.1.8)
 [![Discord](https://user-images.githubusercontent.com/7288322/34471967-1df7808a-efbb-11e7-9088-ed0b04151291.png)](https://discord.gg/CTYGPUJ)

 This is the core repository for Prysm, a [Golang](https://golang.org/) implementation of the [Ethereum Consensus](https://ethereum.org/en/eth2/) specification, developed by [Prysmatic Labs](https://prysmaticlabs.com). See the [Changelog](https://github.com/prysmaticlabs/prysm/releases) for details of the latest releases and upcoming breaking changes.
--- a/64
+++ b/64
@@ -60,10 +60,10 @@ bazel_skylib_workspace()

 http_archive(
    name = "bazel_gazelle",
-    sha256 = "62ca106be173579c0a167deb23358fdfe71ffa1e4cfdddf5582af26520f1c66f",
+    sha256 = "de69a09dc70417580aabf20a28619bb3ef60d038470c7cf8442fafcf627c21cb",
    urls = [
-        "https://mirror.bazel.build/github.com/bazelbuild/bazel-gazelle/releases/download/v0.23.0/bazel-gazelle-v0.23.0.tar.gz",
-        "https://github.com/bazelbuild/bazel-gazelle/releases/download/v0.23.0/bazel-gazelle-v0.23.0.tar.gz",
+        "https://mirror.bazel.build/github.com/bazelbuild/bazel-gazelle/releases/download/v0.24.0/bazel-gazelle-v0.24.0.tar.gz",
+        "https://github.com/bazelbuild/bazel-gazelle/releases/download/v0.24.0/bazel-gazelle-v0.24.0.tar.gz",
    ],
 )

@@ -85,16 +85,13 @@ http_archive(
    name = "io_bazel_rules_go",
    patch_args = ["-p1"],
    patches = [
-        # Required until https://github.com/bazelbuild/rules_go/pull/2450 merges otherwise nilness
-        # nogo check fails for certain third_party dependencies.
-        "//third_party:io_bazel_rules_go.patch",
        # Expose internals of go_test for custom build transitions.
        "//third_party:io_bazel_rules_go_test.patch",
    ],
-    sha256 = "7c10271940c6bce577d51a075ae77728964db285dac0a46614a7934dc34303e6",
+    sha256 = "2b1641428dff9018f9e85c0384f03ec6c10660d935b750e3fa1492a281a53b0f",
    urls = [
-        "https://mirror.bazel.build/github.com/bazelbuild/rules_go/releases/download/v0.26.0/rules_go-v0.26.0.tar.gz",
-        "https://github.com/bazelbuild/rules_go/releases/download/v0.26.0/rules_go-v0.26.0.tar.gz",
+        "https://mirror.bazel.build/github.com/bazelbuild/rules_go/releases/download/v0.29.0/rules_go-v0.29.0.zip",
+        "https://github.com/bazelbuild/rules_go/releases/download/v0.29.0/rules_go-v0.29.0.zip",
    ],
 )

@@ -120,13 +117,6 @@ http_archive(
    urls = ["https://github.com/fuzzitdev/fuzzit/releases/download/v2.4.76/fuzzit_Linux_x86_64.zip"],
 )

-git_repository(
-    name = "graknlabs_bazel_distribution",
-    commit = "962f3a7e56942430c0ec120c24f9e9f2a9c2ce1a",
-    remote = "https://github.com/graknlabs/bazel-distribution",
-    shallow_since = "1569509514 +0300",
-)
-
 load(
    "@io_bazel_rules_docker//repositories:repositories.bzl",
    container_repositories = "repositories",
@@ -186,7 +176,7 @@ load("@io_bazel_rules_go//go:deps.bzl", "go_register_toolchains", "go_rules_depe
 go_rules_dependencies()

 go_register_toolchains(
-    go_version = "1.16.4",
+    go_version = "1.17.6",
    nogo = "@//:nogo",
 )

@@ -222,10 +212,10 @@ filegroup(
 )
    """,
    sha256 = "91434d5fd5e1c6eb7b0174fed2afe25e09bddf00e1e4c431db931b2cee4e7773",
-    url = "https://github.com/eth2-clients/slashing-protection-interchange-tests/archive/b8413ca42dc92308019d0d4db52c87e9e125c4e9.tar.gz",
+    url = "https://github.com/eth-clients/slashing-protection-interchange-tests/archive/b8413ca42dc92308019d0d4db52c87e9e125c4e9.tar.gz",
 )

-consensus_spec_version = "v1.1.0"
+consensus_spec_version = "v1.1.10"

 bls_test_version = "v0.1.1"

@@ -241,7 +231,7 @@ filegroup(
    visibility = ["//visibility:public"],
 )
    """,
-    sha256 = "0f58ec1c8995ab2c0a3aada873e1a02f333c8659fdacaa1c76fbdce28b6177dc",
+    sha256 = "28043009cc2f6fc9804e73c8c1fc2cb27062f1591e6884f3015ae1dd7a276883",
    url = "https://github.com/ethereum/consensus-spec-tests/releases/download/%s/general.tar.gz" % consensus_spec_version,
 )

@@ -257,7 +247,7 @@ filegroup(
    visibility = ["//visibility:public"],
 )
    """,
-    sha256 = "d2eeadef3f8885748f769a06eb916bea60fb00112a90cec3288ea78db5557df3",
+    sha256 = "bc1a283ca068f310f04d70c4f6a8eaa0b8f7e9318073a8bdc2ee233111b4e339",
    url = "https://github.com/ethereum/consensus-spec-tests/releases/download/%s/minimal.tar.gz" % consensus_spec_version,
 )

@@ -273,7 +263,7 @@ filegroup(
    visibility = ["//visibility:public"],
 )
    """,
-    sha256 = "bbc345432f4eaa4babe2619e16fcf3f607113ede82d1bd0fff2633c1376419f7",
+    sha256 = "bbabb482c229ff9d4e2c7b77c992edb452f9d0af7c6d8dd4f922f06a7b101e81",
    url = "https://github.com/ethereum/consensus-spec-tests/releases/download/%s/mainnet.tar.gz" % consensus_spec_version,
 )

@@ -288,7 +278,7 @@ filegroup(
    visibility = ["//visibility:public"],
 )
    """,
-    sha256 = "787a50c2a03bebab92f089333f598780ca7b4849b36a4897e6603ddd3e86ec24",
+    sha256 = "408a5524548ad3fcf387f65ac7ec52781d9ee899499720bb12451b48a15818d4",
    strip_prefix = "consensus-specs-" + consensus_spec_version[1:],
    url = "https://github.com/ethereum/consensus-specs/archive/refs/tags/%s.tar.gz" % consensus_spec_version,
 )
@@ -319,9 +309,9 @@ filegroup(
    visibility = ["//visibility:public"],
 )
    """,
-    sha256 = "9dc47bf6b14aed7fac8833e35ab83a69131b43fa5789b3256bf1ac3d4861aeb8",
-    strip_prefix = "eth2-networks-7fa1b868985ee24aad65567f9250cf7fa86f97b1",
-    url = "https://github.com/eth2-clients/eth2-networks/archive/7fa1b868985ee24aad65567f9250cf7fa86f97b1.tar.gz",
+    sha256 = "4e8a18b21d056c4032605621b1a6632198eabab57cb90c61e273f344c287f1b2",
+    strip_prefix = "eth2-networks-791a5369c5981e829698b17fbcdcdacbdaba97c8",
+    url = "https://github.com/eth-clients/eth2-networks/archive/791a5369c5981e829698b17fbcdcdacbdaba97c8.tar.gz",
 )

 http_archive(
@@ -341,16 +331,6 @@ git_repository(
 # Group the sources of the library so that CMake rule have access to it
 all_content = """filegroup(name = "all", srcs = glob(["**"]), visibility = ["//visibility:public"])"""

-http_archive(
-    name = "sigp_beacon_fuzz_corpora",
-    build_file = "//third_party:beacon-fuzz/corpora.BUILD",
-    sha256 = "42993d0901a316afda45b4ba6d53c7c21f30c551dcec290a4ca131c24453d1ef",
-    strip_prefix = "beacon-fuzz-corpora-bac24ad78d45cc3664c0172241feac969c1ac29b",
-    urls = [
-        "https://github.com/sigp/beacon-fuzz-corpora/archive/bac24ad78d45cc3664c0172241feac969c1ac29b.tar.gz",
-    ],
-)
-
 # External dependencies

 http_archive(
@@ -362,9 +342,9 @@ filegroup(
    visibility = ["//visibility:public"],
 )
 """,
-    sha256 = "54ce527b83d092da01127f2e3816f4d5cfbab69354caba8537f1ea55889b6d7c",
+    sha256 = "4797a7e594a5b1f4c1c8080701613f3ee451b01ec0861499ea7d9b60877a6b23",
    urls = [
-        "https://github.com/prysmaticlabs/prysm-web-ui/releases/download/v1.0.0-beta.4/prysm-web-ui.tar.gz",
+        "https://github.com/prysmaticlabs/prysm-web-ui/releases/download/v1.0.3/prysm-web-ui.tar.gz",
    ],
 )

@@ -377,6 +357,10 @@ load("@prysm//third_party/herumi:herumi.bzl", "bls_dependencies")

 bls_dependencies()

+load("@prysm//testing/endtoend:deps.bzl", "e2e_deps")
+
+e2e_deps()
+
 load(
    "@io_bazel_rules_docker//go:image.bzl",
    _go_image_repos = "repositories",
@@ -395,10 +379,6 @@ load(

 _cc_image_repos()

-load("@com_github_ethereum_go_ethereum//:deps.bzl", "geth_dependencies")
-
-geth_dependencies()
-
 load("@io_bazel_rules_go//extras:embed_data_deps.bzl", "go_embed_data_dependencies")

 go_embed_data_dependencies()
--- a/api/client/beacon/BUILD.bazel
+++ b/api/client/beacon/BUILD.bazel
@@ -0,0 +1,54 @@
+load("@prysm//tools/go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "go_default_library",
+    srcs = [
+        "checkpoint.go",
+        "client.go",
+        "doc.go",
+        "errors.go",
+    ],
+    importpath = "github.com/prysmaticlabs/prysm/api/client/beacon",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//beacon-chain/core/helpers:go_default_library",
+        "//beacon-chain/rpc/apimiddleware:go_default_library",
+        "//beacon-chain/state:go_default_library",
+        "//encoding/bytesutil:go_default_library",
+        "//encoding/ssz/detect:go_default_library",
+        "//io/file:go_default_library",
+        "//network/forks:go_default_library",
+        "//proto/prysm/v1alpha1:go_default_library",
+        "//proto/prysm/v1alpha1/block:go_default_library",
+        "//runtime/version:go_default_library",
+        "//time/slots:go_default_library",
+        "@com_github_ethereum_go_ethereum//common/hexutil:go_default_library",
+        "@com_github_pkg_errors//:go_default_library",
+        "@com_github_prysmaticlabs_eth2_types//:go_default_library",
+        "@com_github_sirupsen_logrus//:go_default_library",
+        "@org_golang_x_mod//semver:go_default_library",
+    ],
+)
+
+go_test(
+    name = "go_default_test",
+    srcs = [
+        "checkpoint_test.go",
+        "client_test.go",
+    ],
+    embed = [":go_default_library"],
+    deps = [
+        "//beacon-chain/state:go_default_library",
+        "//config/params:go_default_library",
+        "//encoding/ssz/detect:go_default_library",
+        "//network/forks:go_default_library",
+        "//proto/prysm/v1alpha1:go_default_library",
+        "//proto/prysm/v1alpha1/wrapper:go_default_library",
+        "//runtime/version:go_default_library",
+        "//testing/require:go_default_library",
+        "//testing/util:go_default_library",
+        "//time/slots:go_default_library",
+        "@com_github_pkg_errors//:go_default_library",
+        "@com_github_prysmaticlabs_eth2_types//:go_default_library",
+    ],
+)
--- a/api/client/beacon/checkpoint.go
+++ b/api/client/beacon/checkpoint.go
@@ -0,0 +1,262 @@
+package beacon
+
+import (
+	"context"
+	"fmt"
+	"path"
+
+	"github.com/pkg/errors"
+	types "github.com/prysmaticlabs/eth2-types"
+	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
+	"github.com/prysmaticlabs/prysm/beacon-chain/state"
+	"github.com/prysmaticlabs/prysm/encoding/ssz/detect"
+	"github.com/prysmaticlabs/prysm/io/file"
+	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/block"
+	"github.com/prysmaticlabs/prysm/runtime/version"
+	"github.com/prysmaticlabs/prysm/time/slots"
+	log "github.com/sirupsen/logrus"
+	"golang.org/x/mod/semver"
+)
+
+// OriginData represents the BeaconState and SignedBeaconBlock necessary to start an empty Beacon Node
+// using Checkpoint Sync.
+type OriginData struct {
+	wsd *WeakSubjectivityData
+	sb  []byte
+	bb  []byte
+	st  state.BeaconState
+	b   block.SignedBeaconBlock
+	cf  *detect.VersionedUnmarshaler
+}
+
+// CheckpointString returns the standard string representation of a Checkpoint for the block root and epoch for the
+// SignedBeaconBlock value found by DownloadOriginData.
+// The format is a a hex-encoded block root, followed by the epoch of the block, separated by a colon. For example:
+// "0x1c35540cac127315fabb6bf29181f2ae0de1a3fc909d2e76ba771e61312cc49a:74888"
+func (od *OriginData) CheckpointString() string {
+	return fmt.Sprintf("%#x:%d", od.wsd.BlockRoot, od.wsd.Epoch)
+}
+
+// SaveBlock saves the downloaded block to a unique file in the given path.
+// For readability and collision avoidance, the file name includes: type, config name, slot and root
+func (od *OriginData) SaveBlock(dir string) (string, error) {
+	blockPath := path.Join(dir, fname("state", od.cf, od.st.Slot(), od.wsd.BlockRoot))
+	return blockPath, file.WriteFile(blockPath, od.sb)
+}
+
+// SaveState saves the downloaded state to a unique file in the given path.
+// For readability and collision avoidance, the file name includes: type, config name, slot and root
+func (od *OriginData) SaveState(dir string) (string, error) {
+	statePath := path.Join(dir, fname("state", od.cf, od.st.Slot(), od.wsd.StateRoot))
+	return statePath, file.WriteFile(statePath, od.sb)
+}
+
+// StateBytes returns the ssz-encoded bytes of the downloaded BeaconState value.
+func (od *OriginData) StateBytes() []byte {
+	return od.sb
+}
+
+// BlockBytes returns the ssz-encoded bytes of the downloaded SignedBeaconBlock value.
+func (od *OriginData) BlockBytes() []byte {
+	return od.bb
+}
+
+func fname(prefix string, cf *detect.VersionedUnmarshaler, slot types.Slot, root [32]byte) string {
+	return fmt.Sprintf("%s_%s_%s_%d-%#x.ssz", prefix, cf.Config.ConfigName, version.String(cf.Fork), slot, root)
+}
+
+// this method downloads the head state, which can be used to find the correct chain config
+// and use prysm's helper methods to compute the latest weak subjectivity epoch.
+func getWeakSubjectivityEpochFromHead(ctx context.Context, client *Client) (types.Epoch, error) {
+	headBytes, err := client.GetState(ctx, IdHead)
+	if err != nil {
+		return 0, err
+	}
+	cf, err := detect.FromState(headBytes)
+	if err != nil {
+		return 0, errors.Wrap(err, "error detecting chain config for beacon state")
+	}
+	log.Printf("detected supported config in remote head state, name=%s, fork=%s", cf.Config.ConfigName, version.String(cf.Fork))
+	headState, err := cf.UnmarshalBeaconState(headBytes)
+	if err != nil {
+		return 0, errors.Wrap(err, "error unmarshaling state to correct version")
+	}
+
+	epoch, err := helpers.LatestWeakSubjectivityEpoch(ctx, headState, cf.Config)
+	if err != nil {
+		return 0, errors.Wrap(err, "error computing the weak subjectivity epoch from head state")
+	}
+
+	log.Printf("(computed client-side) weak subjectivity epoch = %d", epoch)
+	return epoch, nil
+}
+
+const (
+	prysmMinimumVersion     = "v2.0.7"
+	prysmImplementationName = "Prysm"
+)
+
+// ErrUnsupportedPrysmCheckpointVersion indicates remote beacon node can't be used for checkpoint retrieval.
+var ErrUnsupportedPrysmCheckpointVersion = errors.New("node does not meet minimum version requirements for checkpoint retrieval")
+
+// for older endpoints or clients that do not support the weak_subjectivity api method
+// we gather the necessary data for a checkpoint sync by:
+// - inspecting the remote server's head state and computing the weak subjectivity epoch locally
+// - requesting the state at the first slot of the epoch
+// - using hash_tree_root(state.latest_block_header) to compute the block the state integrates
+// - requesting that block by its root
+func downloadBackwardsCompatible(ctx context.Context, client *Client) (*OriginData, error) {
+	log.Print("falling back to generic checkpoint derivation, weak_subjectivity API not supported by server")
+	nv, err := client.GetNodeVersion(ctx)
+	if err != nil {
+		return nil, errors.Wrap(err, "unable to proceed with fallback method without confirming node version")
+	}
+	if nv.implementation == prysmImplementationName && semver.Compare(nv.semver, prysmMinimumVersion) < 0 {
+		return nil, errors.Wrapf(ErrUnsupportedPrysmCheckpointVersion, "%s < minimum (%s)", nv.semver, prysmMinimumVersion)
+	}
+	epoch, err := getWeakSubjectivityEpochFromHead(ctx, client)
+	if err != nil {
+		return nil, errors.Wrap(err, "error computing weak subjectivity epoch via head state inspection")
+	}
+
+	// use first slot of the epoch for the state slot
+	slot, err := slots.EpochStart(epoch)
+	if err != nil {
+		return nil, errors.Wrapf(err, "error computing first slot of epoch=%d", epoch)
+	}
+
+	log.Printf("requesting checkpoint state at slot %d", slot)
+	// get the state at the first slot of the epoch
+	stateBytes, err := client.GetState(ctx, IdFromSlot(slot))
+	if err != nil {
+		return nil, errors.Wrapf(err, "failed to request state by slot from api, slot=%d", slot)
+	}
+
+	// ConfigFork is used to unmarshal the BeaconState so we can read the block root in latest_block_header
+	cf, err := detect.FromState(stateBytes)
+	if err != nil {
+		return nil, errors.Wrap(err, "error detecting chain config for beacon state")
+	}
+	log.Printf("detected supported config in checkpoint state, name=%s, fork=%s", cf.Config.ConfigName, version.String(cf.Fork))
+
+	st, err := cf.UnmarshalBeaconState(stateBytes)
+	if err != nil {
+		return nil, errors.Wrap(err, "error using detected config fork to unmarshal state bytes")
+	}
+
+	// compute state and block roots
+	stateRoot, err := st.HashTreeRoot(ctx)
+	if err != nil {
+		return nil, errors.Wrap(err, "error computing hash_tree_root of state")
+	}
+
+	header := st.LatestBlockHeader()
+	header.StateRoot = stateRoot[:]
+	computedBlockRoot, err := header.HashTreeRoot()
+	if err != nil {
+		return nil, errors.Wrap(err, "error while computing block root using state data")
+	}
+
+	blockBytes, err := client.GetBlock(ctx, IdFromRoot(computedBlockRoot))
+	if err != nil {
+		return nil, errors.Wrapf(err, "error requesting block by root = %d", computedBlockRoot)
+	}
+	block, err := cf.UnmarshalBeaconBlock(blockBytes)
+	if err != nil {
+		return nil, errors.Wrap(err, "unable to unmarshal block to a supported type using the detected fork schedule")
+	}
+	blockRoot, err := block.Block().HashTreeRoot()
+	if err != nil {
+		return nil, errors.Wrap(err, "error computing hash_tree_root for block obtained via root")
+	}
+
+	log.Printf("BeaconState slot=%d, Block slot=%d", st.Slot(), block.Block().Slot())
+	log.Printf("BeaconState htr=%#xd, Block state_root=%#x", stateRoot, block.Block().StateRoot())
+	log.Printf("BeaconBlock root computed from state=%#x, Block htr=%#x", computedBlockRoot, blockRoot)
+
+	return &OriginData{
+		wsd: &WeakSubjectivityData{
+			BlockRoot: blockRoot,
+			StateRoot: stateRoot,
+			Epoch:     epoch,
+		},
+		st: st,
+		sb: stateBytes,
+		b:  block,
+		bb: blockBytes,
+		cf: cf,
+	}, nil
+}
+
+// DownloadOriginData attempts to use the proposed weak_subjectivity beacon node api
+// to obtain the weak_subjectivity metadata (epoch, block_root, state_root) needed to sync
+// a beacon node from the canonical weak subjectivity checkpoint. As this is a proposed API
+// that will only be supported by prysm at first, in the event of a 404 we fallback to using a
+// different technique where we first download the head state which can be used to compute the
+// weak subjectivity epoch on the client side.
+func DownloadOriginData(ctx context.Context, client *Client) (*OriginData, error) {
+	ws, err := client.GetWeakSubjectivity(ctx)
+	if err != nil {
+		// a 404/405 is expected if querying an endpoint that doesn't support the weak subjectivity checkpoint api
+		if !errors.Is(err, ErrNotOK) {
+			return nil, errors.Wrap(err, "unexpected API response for prysm-only weak subjectivity checkpoint API")
+		}
+		// fall back to vanilla Beacon Node API method
+		return downloadBackwardsCompatible(ctx, client)
+	}
+	log.Printf("server weak subjectivity checkpoint response - epoch=%d, block_root=%#x, state_root=%#x", ws.Epoch, ws.BlockRoot, ws.StateRoot)
+
+	// use first slot of the epoch for the block slot
+	slot, err := slots.EpochStart(ws.Epoch)
+	if err != nil {
+		return nil, errors.Wrapf(err, "error computing first slot of epoch=%d", ws.Epoch)
+	}
+	log.Printf("requesting checkpoint state at slot %d", slot)
+
+	stateBytes, err := client.GetState(ctx, IdFromSlot(slot))
+	if err != nil {
+		return nil, errors.Wrapf(err, "failed to request state by slot from api, slot=%d", slot)
+	}
+	cf, err := detect.FromState(stateBytes)
+	if err != nil {
+		return nil, errors.Wrap(err, "error detecting chain config for beacon state")
+	}
+	log.Printf("detected supported config in checkpoint state, name=%s, fork=%s", cf.Config.ConfigName, version.String(cf.Fork))
+
+	state, err := cf.UnmarshalBeaconState(stateBytes)
+	if err != nil {
+		return nil, errors.Wrap(err, "error using detected config fork to unmarshal state bytes")
+	}
+	stateRoot, err := state.HashTreeRoot(ctx)
+	if err != nil {
+		return nil, errors.Wrapf(err, "failed to compute htr for state at slot=%d", slot)
+	}
+
+	blockRoot, err := state.LatestBlockHeader().HashTreeRoot()
+	if err != nil {
+		return nil, errors.Wrap(err, "error computing hash_tree_root of latest_block_header")
+	}
+	blockBytes, err := client.GetBlock(ctx, IdFromRoot(ws.BlockRoot))
+	if err != nil {
+		return nil, errors.Wrapf(err, "error requesting block by slot = %d", slot)
+	}
+	block, err := cf.UnmarshalBeaconBlock(blockBytes)
+	if err != nil {
+		return nil, errors.Wrap(err, "unable to unmarshal block to a supported type using the detected fork schedule")
+	}
+	realBlockRoot, err := block.Block().HashTreeRoot()
+	if err != nil {
+		return nil, errors.Wrap(err, "error computing hash_tree_root of retrieved block")
+	}
+	log.Printf("BeaconState slot=%d, Block slot=%d", state.Slot(), block.Block().Slot())
+	log.Printf("BeaconState htr=%#xd, Block state_root=%#x", stateRoot, block.Block().StateRoot())
+	log.Printf("BeaconState latest_block_header htr=%#xd, block htr=%#x", blockRoot, realBlockRoot)
+	return &OriginData{
+		wsd: ws,
+		st:  state,
+		b:   block,
+		sb:  stateBytes,
+		bb:  blockBytes,
+		cf:  cf,
+	}, nil
+}
--- a/api/client/beacon/checkpoint_test.go
+++ b/api/client/beacon/checkpoint_test.go
@@ -0,0 +1,407 @@
+package beacon
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"testing"
+
+	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/wrapper"
+
+	"github.com/prysmaticlabs/prysm/beacon-chain/state"
+	"github.com/prysmaticlabs/prysm/network/forks"
+	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
+	"github.com/prysmaticlabs/prysm/testing/util"
+	"github.com/prysmaticlabs/prysm/time/slots"
+
+	types "github.com/prysmaticlabs/eth2-types"
+	"github.com/prysmaticlabs/prysm/config/params"
+	"github.com/prysmaticlabs/prysm/encoding/ssz/detect"
+	"github.com/prysmaticlabs/prysm/runtime/version"
+
+	"github.com/pkg/errors"
+	"github.com/prysmaticlabs/prysm/testing/require"
+)
+
+type testRT struct {
+	rt func(*http.Request) (*http.Response, error)
+}
+
+func (rt *testRT) RoundTrip(req *http.Request) (*http.Response, error) {
+	if rt.rt != nil {
+		return rt.rt(req)
+	}
+	return nil, errors.New("RoundTripper not implemented")
+}
+
+var _ http.RoundTripper = &testRT{}
+
+func marshalToEnvelope(val interface{}) ([]byte, error) {
+	raw, err := json.Marshal(val)
+	if err != nil {
+		return nil, errors.Wrap(err, "error marshaling value to place in data envelope")
+	}
+	env := struct {
+		Data json.RawMessage `json:"data"`
+	}{
+		Data: raw,
+	}
+	return json.Marshal(env)
+}
+
+func TestMarshalToEnvelope(t *testing.T) {
+	d := struct {
+		Version string `json:"version"`
+	}{
+		Version: "Prysm/v2.0.5 (linux amd64)",
+	}
+	encoded, err := marshalToEnvelope(d)
+	require.NoError(t, err)
+	expected := `{"data":{"version":"Prysm/v2.0.5 (linux amd64)"}}`
+	require.Equal(t, expected, string(encoded))
+}
+
+func TestFallbackVersionCheck(t *testing.T) {
+	c := &Client{
+		hc:     &http.Client{},
+		host:   "localhost:3500",
+		scheme: "http",
+	}
+	c.hc.Transport = &testRT{rt: func(req *http.Request) (*http.Response, error) {
+		res := &http.Response{Request: req}
+		switch req.URL.Path {
+		case getNodeVersionPath:
+			res.StatusCode = http.StatusOK
+			b := bytes.NewBuffer(nil)
+			d := struct {
+				Version string `json:"version"`
+			}{
+				Version: "Prysm/v2.0.5 (linux amd64)",
+			}
+			encoded, err := marshalToEnvelope(d)
+			require.NoError(t, err)
+			b.Write(encoded)
+			res.Body = io.NopCloser(b)
+		case getWeakSubjectivityPath:
+			res.StatusCode = http.StatusNotFound
+		}
+
+		return res, nil
+	}}
+
+	ctx := context.Background()
+	_, err := DownloadOriginData(ctx, c)
+	require.ErrorIs(t, err, ErrUnsupportedPrysmCheckpointVersion)
+}
+
+func TestFname(t *testing.T) {
+	vu := &detect.VersionedUnmarshaler{
+		Config: params.MainnetConfig(),
+		Fork:   version.Phase0,
+	}
+	slot := types.Slot(23)
+	prefix := "block"
+	var root [32]byte
+	copy(root[:], []byte{0x23, 0x23, 0x23})
+	expected := "block_mainnet_phase0_23-0x2323230000000000000000000000000000000000000000000000000000000000.ssz"
+	actual := fname(prefix, vu, slot, root)
+	require.Equal(t, expected, actual)
+
+	vu.Config = params.MinimalSpecConfig()
+	vu.Fork = version.Altair
+	slot = 17
+	prefix = "state"
+	copy(root[29:], []byte{0x17, 0x17, 0x17})
+	expected = "state_minimal_altair_17-0x2323230000000000000000000000000000000000000000000000000000171717.ssz"
+	actual = fname(prefix, vu, slot, root)
+	require.Equal(t, expected, actual)
+}
+
+func TestDownloadOriginData(t *testing.T) {
+	ctx := context.Background()
+	cfg := params.MainnetConfig()
+
+	epoch := cfg.AltairForkEpoch - 1
+	// set up checkpoint state, using the epoch that will be computed as the ws checkpoint state based on the head state
+	wSlot, err := slots.EpochStart(epoch)
+	require.NoError(t, err)
+	wst, err := util.NewBeaconState()
+	require.NoError(t, err)
+	fork, err := forkForEpoch(cfg, epoch)
+	require.NoError(t, wst.SetFork(fork))
+
+	// set up checkpoint block
+	b, err := wrapper.WrappedSignedBeaconBlock(util.NewBeaconBlock())
+	require.NoError(t, wrapper.SetBlockParentRoot(b, cfg.ZeroHash))
+	require.NoError(t, wrapper.SetBlockSlot(b, wSlot))
+	require.NoError(t, wrapper.SetProposerIndex(b, 0))
+
+	// set up state header pointing at checkpoint block - this is how the block is downloaded by root
+	header, err := b.Header()
+	require.NoError(t, err)
+	require.NoError(t, wst.SetLatestBlockHeader(header.Header))
+
+	// order of operations can be confusing here:
+	// - when computing the state root, make sure block header is complete, EXCEPT the state root should be zero-value
+	// - before computing the block root (to match the request route), the block should include the state root
+	//   *computed from the state with a header that does not have a state root set yet*
+	wRoot, err := wst.HashTreeRoot(ctx)
+	require.NoError(t, err)
+
+	require.NoError(t, wrapper.SetBlockStateRoot(b, wRoot))
+	serBlock, err := b.MarshalSSZ()
+	require.NoError(t, err)
+	bRoot, err := b.Block().HashTreeRoot()
+	require.NoError(t, err)
+
+	wsSerialized, err := wst.MarshalSSZ()
+	require.NoError(t, err)
+	expectedWSD := WeakSubjectivityData{
+		BlockRoot: bRoot,
+		StateRoot: wRoot,
+		Epoch:     epoch,
+	}
+
+	hc := &http.Client{
+		Transport: &testRT{rt: func(req *http.Request) (*http.Response, error) {
+			res := &http.Response{Request: req}
+			switch req.URL.Path {
+			case getWeakSubjectivityPath:
+				res.StatusCode = http.StatusOK
+				cp := struct {
+					Epoch string `json:"epoch"`
+					Root  string `json:"root"`
+				}{
+					Epoch: fmt.Sprintf("%d", slots.ToEpoch(b.Block().Slot())),
+					Root:  fmt.Sprintf("%#x", bRoot),
+				}
+				wsr := struct {
+					Checkpoint interface{} `json:"ws_checkpoint"`
+					StateRoot  string      `json:"state_root"`
+				}{
+					Checkpoint: cp,
+					StateRoot:  fmt.Sprintf("%#x", wRoot),
+				}
+				rb, err := marshalToEnvelope(wsr)
+				require.NoError(t, err)
+				res.Body = io.NopCloser(bytes.NewBuffer(rb))
+			case renderGetStatePath(IdFromSlot(wSlot)):
+				res.StatusCode = http.StatusOK
+				res.Body = io.NopCloser(bytes.NewBuffer(wsSerialized))
+			case renderGetBlockPath(IdFromRoot(bRoot)):
+				res.StatusCode = http.StatusOK
+				res.Body = io.NopCloser(bytes.NewBuffer(serBlock))
+			}
+
+			return res, nil
+		}},
+	}
+	c := &Client{
+		hc:     hc,
+		host:   "localhost:3500",
+		scheme: "http",
+	}
+
+	od, err := DownloadOriginData(ctx, c)
+	require.NoError(t, err)
+	require.Equal(t, expectedWSD.Epoch, od.wsd.Epoch)
+	require.Equal(t, expectedWSD.StateRoot, od.wsd.StateRoot)
+	require.Equal(t, expectedWSD.BlockRoot, od.wsd.BlockRoot)
+	require.DeepEqual(t, wsSerialized, od.sb)
+	require.DeepEqual(t, serBlock, od.bb)
+	require.DeepEqual(t, wst.Fork().CurrentVersion, od.cf.Version[:])
+	require.DeepEqual(t, version.Phase0, od.cf.Fork)
+}
+
+// runs downloadBackwardsCompatible directly
+// and via DownloadOriginData with a round tripper that triggers the backwards compatible code path
+func TestDownloadBackwardsCompatibleCombined(t *testing.T) {
+	ctx := context.Background()
+	cfg := params.MainnetConfig()
+
+	st, expectedEpoch := defaultTestHeadState(t, cfg)
+	serialized, err := st.MarshalSSZ()
+	require.NoError(t, err)
+
+	// set up checkpoint state, using the epoch that will be computed as the ws checkpoint state based on the head state
+	wSlot, err := slots.EpochStart(expectedEpoch)
+	require.NoError(t, err)
+	wst, err := util.NewBeaconState()
+	require.NoError(t, err)
+	fork, err := forkForEpoch(cfg, cfg.GenesisEpoch)
+	require.NoError(t, wst.SetFork(fork))
+
+	// set up checkpoint block
+	b, err := wrapper.WrappedSignedBeaconBlock(util.NewBeaconBlock())
+	require.NoError(t, wrapper.SetBlockParentRoot(b, cfg.ZeroHash))
+	require.NoError(t, wrapper.SetBlockSlot(b, wSlot))
+	require.NoError(t, wrapper.SetProposerIndex(b, 0))
+
+	// set up state header pointing at checkpoint block - this is how the block is downloaded by root
+	header, err := b.Header()
+	require.NoError(t, err)
+	require.NoError(t, wst.SetLatestBlockHeader(header.Header))
+
+	// order of operations can be confusing here:
+	// - when computing the state root, make sure block header is complete, EXCEPT the state root should be zero-value
+	// - before computing the block root (to match the request route), the block should include the state root
+	//   *computed from the state with a header that does not have a state root set yet*
+	wRoot, err := wst.HashTreeRoot(ctx)
+	require.NoError(t, err)
+
+	require.NoError(t, wrapper.SetBlockStateRoot(b, wRoot))
+	serBlock, err := b.MarshalSSZ()
+	require.NoError(t, err)
+	bRoot, err := b.Block().HashTreeRoot()
+	require.NoError(t, err)
+
+	wsSerialized, err := wst.MarshalSSZ()
+	require.NoError(t, err)
+
+	hc := &http.Client{
+		Transport: &testRT{rt: func(req *http.Request) (*http.Response, error) {
+			res := &http.Response{Request: req}
+			switch req.URL.Path {
+			case getNodeVersionPath:
+				res.StatusCode = http.StatusOK
+				b := bytes.NewBuffer(nil)
+				d := struct {
+					Version string `json:"version"`
+				}{
+					Version: "Lighthouse/v0.1.5 (Linux x86_64)",
+				}
+				encoded, err := marshalToEnvelope(d)
+				require.NoError(t, err)
+				b.Write(encoded)
+				res.Body = io.NopCloser(b)
+			case getWeakSubjectivityPath:
+				res.StatusCode = http.StatusNotFound
+			case renderGetStatePath(IdHead):
+				res.StatusCode = http.StatusOK
+				res.Body = io.NopCloser(bytes.NewBuffer(serialized))
+			case renderGetStatePath(IdFromSlot(wSlot)):
+				res.StatusCode = http.StatusOK
+				res.Body = io.NopCloser(bytes.NewBuffer(wsSerialized))
+			case renderGetBlockPath(IdFromRoot(bRoot)):
+				res.StatusCode = http.StatusOK
+				res.Body = io.NopCloser(bytes.NewBuffer(serBlock))
+			}
+
+			return res, nil
+		}},
+	}
+	c := &Client{
+		hc:     hc,
+		host:   "localhost:3500",
+		scheme: "http",
+	}
+
+	odPub, err := DownloadOriginData(ctx, c)
+	require.NoError(t, err)
+
+	odPriv, err := downloadBackwardsCompatible(ctx, c)
+	require.NoError(t, err)
+	require.DeepEqual(t, odPriv.wsd, odPub.wsd)
+	require.DeepEqual(t, odPriv.sb, odPub.sb)
+	require.DeepEqual(t, odPriv.bb, odPub.bb)
+	require.DeepEqual(t, odPriv.cf.Fork, odPub.cf.Fork)
+	require.DeepEqual(t, odPriv.cf.Version, odPub.cf.Version)
+}
+
+func TestGetWeakSubjectivityEpochFromHead(t *testing.T) {
+	st, expectedEpoch := defaultTestHeadState(t, params.MainnetConfig())
+	serialized, err := st.MarshalSSZ()
+	require.NoError(t, err)
+	hc := &http.Client{
+		Transport: &testRT{rt: func(req *http.Request) (*http.Response, error) {
+			res := &http.Response{Request: req}
+			switch req.URL.Path {
+			case renderGetStatePath(IdHead):
+				res.StatusCode = http.StatusOK
+				res.Body = io.NopCloser(bytes.NewBuffer(serialized))
+			}
+			return res, nil
+		}},
+	}
+	c := &Client{
+		hc:     hc,
+		host:   "localhost:3500",
+		scheme: "http",
+	}
+	actualEpoch, err := getWeakSubjectivityEpochFromHead(context.Background(), c)
+	require.NoError(t, err)
+	require.Equal(t, expectedEpoch, actualEpoch)
+}
+
+func forkForEpoch(cfg *params.BeaconChainConfig, epoch types.Epoch) (*ethpb.Fork, error) {
+	os := forks.NewOrderedSchedule(cfg)
+	currentVersion, err := os.VersionForEpoch(epoch)
+	if err != nil {
+		return nil, err
+	}
+	prevVersion, err := os.Previous(currentVersion)
+	if err != nil {
+		if !errors.Is(err, forks.ErrNoPreviousVersion) {
+			return nil, err
+		}
+		// use same version for both in the case of genesis
+		prevVersion = currentVersion
+	}
+	forkEpoch := cfg.ForkVersionSchedule[currentVersion]
+	return &ethpb.Fork{
+		PreviousVersion: prevVersion[:],
+		CurrentVersion:  currentVersion[:],
+		Epoch:           forkEpoch,
+	}, nil
+}
+
+func defaultTestHeadState(t *testing.T, cfg *params.BeaconChainConfig) (state.BeaconState, types.Epoch) {
+	st, err := util.NewBeaconStateAltair()
+	require.NoError(t, err)
+
+	fork, err := forkForEpoch(cfg, cfg.AltairForkEpoch)
+	require.NoError(t, err)
+	require.NoError(t, st.SetFork(fork))
+
+	slot, err := slots.EpochStart(cfg.AltairForkEpoch)
+	require.NoError(t, err)
+	require.NoError(t, st.SetSlot(slot))
+
+	var validatorCount, avgBalance uint64 = 100, 35
+	require.NoError(t, populateValidators(cfg, st, validatorCount, avgBalance))
+	require.NoError(t, st.SetFinalizedCheckpoint(&ethpb.Checkpoint{
+		Epoch: fork.Epoch - 10,
+		Root:  make([]byte, 32),
+	}))
+	// to see the math for this, look at helpers.LatestWeakSubjectivityEpoch
+	// and for the values use mainnet config values, the validatorCount and avgBalance above, and altair fork epoch
+	expectedEpoch := slots.ToEpoch(st.Slot()) - 224
+	return st, expectedEpoch
+}
+
+// TODO(10429): refactor beacon state options in testing/util to take a state.BeaconState so this can become an option
+func populateValidators(cfg *params.BeaconChainConfig, st state.BeaconState, valCount, avgBalance uint64) error {
+	validators := make([]*ethpb.Validator, valCount)
+	balances := make([]uint64, len(validators))
+	for i := uint64(0); i < valCount; i++ {
+		validators[i] = &ethpb.Validator{
+			PublicKey:             make([]byte, cfg.BLSPubkeyLength),
+			WithdrawalCredentials: make([]byte, 32),
+			EffectiveBalance:      avgBalance * 1e9,
+			ExitEpoch:             cfg.FarFutureEpoch,
+		}
+		balances[i] = validators[i].EffectiveBalance
+	}
+
+	if err := st.SetValidators(validators); err != nil {
+		return err
+	}
+	if err := st.SetBalances(balances); err != nil {
+		return err
+	}
+
+	return nil
+}
--- a/api/client/beacon/client.go
+++ b/api/client/beacon/client.go
@@ -0,0 +1,437 @@
+package beacon
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"net/url"
+	"path"
+	"regexp"
+	"sort"
+	"strconv"
+	"text/template"
+	"time"
+
+	"github.com/prysmaticlabs/prysm/network/forks"
+
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/pkg/errors"
+	types "github.com/prysmaticlabs/eth2-types"
+	"github.com/prysmaticlabs/prysm/beacon-chain/rpc/apimiddleware"
+	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
+	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
+	log "github.com/sirupsen/logrus"
+)
+
+const (
+	getSignedBlockPath      = "/eth/v2/beacon/blocks"
+	getBlockRootPath        = "/eth/v1/beacon/blocks/{{.Id}}/root"
+	getForkForStatePath     = "/eth/v1/beacon/states/{{.Id}}/fork"
+	getWeakSubjectivityPath = "/eth/v1/beacon/weak_subjectivity"
+	getForkSchedulePath     = "/eth/v1/config/fork_schedule"
+	getStatePath            = "/eth/v2/debug/beacon/states"
+	getNodeVersionPath      = "/eth/v1/node/version"
+)
+
+// StateOrBlockId represents the block_id / state_id parameters that several of the Eth Beacon API methods accept.
+// StateOrBlockId constants are defined for named identifiers, and helper methods are provided
+// for slot and root identifiers. Example text from the Eth Beacon Node API documentation:
+//
+// "Block identifier can be one of: "head" (canonical head in node's view), "genesis", "finalized",
+// <slot>, <hex encoded blockRoot with 0x prefix>."
+type StateOrBlockId string
+
+const (
+	IdFinalized StateOrBlockId = "finalized"
+	IdGenesis   StateOrBlockId = "genesis"
+	IdHead      StateOrBlockId = "head"
+	IdJustified StateOrBlockId = "justified"
+)
+
+// IdFromRoot encodes a block root in the format expected by the API in places where a root can be used to identify
+// a BeaconState or SignedBeaconBlock.
+func IdFromRoot(r [32]byte) StateOrBlockId {
+	return StateOrBlockId(fmt.Sprintf("%#x", r))
+}
+
+// IdFromRoot encodes a Slot in the format expected by the API in places where a slot can be used to identify
+// a BeaconState or SignedBeaconBlock.
+func IdFromSlot(s types.Slot) StateOrBlockId {
+	return StateOrBlockId(strconv.FormatUint(uint64(s), 10))
+}
+
+// idTemplate is used to create template functions that can interpolate StateOrBlockId values.
+func idTemplate(ts string) func(StateOrBlockId) string {
+	t := template.Must(template.New("").Parse(ts))
+	f := func(id StateOrBlockId) string {
+		b := bytes.NewBuffer(nil)
+		err := t.Execute(b, struct{ Id string }{Id: string(id)})
+		if err != nil {
+			panic(fmt.Sprintf("invalid idTemplate: %s", ts))
+		}
+		return b.String()
+	}
+	// run the template to ensure that it is valid
+	// this should happen load time (using package scoped vars) to ensure runtime errors aren't possible
+	_ = f(IdGenesis)
+	return f
+}
+
+// ClientOpt is a functional option for the Client type (http.Client wrapper)
+type ClientOpt func(*Client)
+
+// WithTimeout sets the .Timeout attribute of the wrapped http.Client.
+func WithTimeout(timeout time.Duration) ClientOpt {
+	return func(c *Client) {
+		c.hc.Timeout = timeout
+	}
+}
+
+// Client provides a collection of helper methods for calling the Eth Beacon Node API endpoints.
+type Client struct {
+	hc     *http.Client
+	host   string
+	scheme string
+}
+
+// NewClient constructs a new client with the provided options (ex WithTimeout).
+// `host` is the base host + port used to construct request urls. This value can be
+// a URL string, or NewClient will assume an http endpoint if just `host:port` is used.
+func NewClient(host string, opts ...ClientOpt) (*Client, error) {
+	host, err := validHostname(host)
+	if err != nil {
+		return nil, err
+	}
+	c := &Client{
+		hc:     &http.Client{},
+		scheme: "http",
+		host:   host,
+	}
+	for _, o := range opts {
+		o(c)
+	}
+	return c, nil
+}
+
+func validHostname(h string) (string, error) {
+	// try to parse as url (being permissive)
+	u, err := url.Parse(h)
+	if err == nil && u.Host != "" {
+		return u.Host, nil
+	}
+	// try to parse as host:port
+	host, port, err := net.SplitHostPort(h)
+	if err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("%s:%s", host, port), nil
+}
+
+func (c *Client) urlForPath(methodPath string) *url.URL {
+	u := &url.URL{
+		Scheme: c.scheme,
+		Host:   c.host,
+	}
+	u.Path = path.Join(u.Path, methodPath)
+	return u
+}
+
+type reqOption func(*http.Request)
+
+func withSSZEncoding() reqOption {
+	return func(req *http.Request) {
+		req.Header.Set("Accept", "application/octet-stream")
+	}
+}
+
+// get is a generic, opinionated GET function to reduce boilerplate amongst the getters in this package.
+func (c *Client) get(ctx context.Context, path string, opts ...reqOption) ([]byte, error) {
+	u := c.urlForPath(path)
+	log.Printf("requesting %s", u.String())
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, u.String(), nil)
+	if err != nil {
+		return nil, err
+	}
+	for _, o := range opts {
+		o(req)
+	}
+	r, err := c.hc.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer func() {
+		err = r.Body.Close()
+	}()
+	if r.StatusCode != http.StatusOK {
+		return nil, non200Err(r)
+	}
+	b, err := io.ReadAll(r.Body)
+	if err != nil {
+		return nil, errors.Wrap(err, "error reading http response body from GetBlock")
+	}
+	return b, nil
+}
+
+func renderGetBlockPath(id StateOrBlockId) string {
+	return path.Join(getSignedBlockPath, string(id))
+}
+
+// GetBlock retrieves the SignedBeaconBlock for the given block id.
+// Block identifier can be one of: "head" (canonical head in node's view), "genesis", "finalized",
+// <slot>, <hex encoded blockRoot with 0x prefix>. Variables of type StateOrBlockId are exported by this package
+// for the named identifiers.
+// The return value contains the ssz-encoded bytes.
+func (c *Client) GetBlock(ctx context.Context, blockId StateOrBlockId) ([]byte, error) {
+	blockPath := renderGetBlockPath(blockId)
+	b, err := c.get(ctx, blockPath, withSSZEncoding())
+	if err != nil {
+		return nil, errors.Wrapf(err, "error requesting state by id = %s", blockId)
+	}
+	return b, nil
+}
+
+var getBlockRootTpl = idTemplate(getBlockRootPath)
+
+// GetBlockRoot retrieves the hash_tree_root of the BeaconBlock for the given block id.
+// Block identifier can be one of: "head" (canonical head in node's view), "genesis", "finalized",
+// <slot>, <hex encoded blockRoot with 0x prefix>. Variables of type StateOrBlockId are exported by this package
+// for the named identifiers.
+func (c *Client) GetBlockRoot(ctx context.Context, blockId StateOrBlockId) ([32]byte, error) {
+	rootPath := getBlockRootTpl(blockId)
+	b, err := c.get(ctx, rootPath)
+	if err != nil {
+		return [32]byte{}, errors.Wrapf(err, "error requesting block root by id = %s", blockId)
+	}
+	jsonr := &struct{ Data struct{ Root string } }{}
+	err = json.Unmarshal(b, jsonr)
+	if err != nil {
+		return [32]byte{}, errors.Wrap(err, "error decoding json data from get block root response")
+	}
+	rs, err := hexutil.Decode(jsonr.Data.Root)
+	if err != nil {
+		return [32]byte{}, errors.Wrap(err, fmt.Sprintf("error decoding hex-encoded value %s", jsonr.Data.Root))
+	}
+	return bytesutil.ToBytes32(rs), nil
+}
+
+var getForkTpl = idTemplate(getForkForStatePath)
+
+// GetFork queries the Beacon Node API for the Fork from the state identified by stateId.
+// Block identifier can be one of: "head" (canonical head in node's view), "genesis", "finalized",
+// <slot>, <hex encoded blockRoot with 0x prefix>. Variables of type StateOrBlockId are exported by this package
+// for the named identifiers.
+func (c *Client) GetFork(ctx context.Context, stateId StateOrBlockId) (*ethpb.Fork, error) {
+	body, err := c.get(ctx, getForkTpl(stateId))
+	if err != nil {
+		return nil, errors.Wrapf(err, "error requesting fork by state id = %s", stateId)
+	}
+	fr := &forkResponse{}
+	dataWrapper := &struct{ Data *forkResponse }{Data: fr}
+	err = json.Unmarshal(body, dataWrapper)
+	if err != nil {
+		return nil, errors.Wrap(err, "error decoding json response in GetFork")
+	}
+
+	return fr.Fork()
+}
+
+// GetForkSchedule retrieve all forks, past present and future, of which this node is aware.
+func (c *Client) GetForkSchedule(ctx context.Context) (forks.OrderedSchedule, error) {
+	body, err := c.get(ctx, getForkSchedulePath)
+	if err != nil {
+		return nil, errors.Wrap(err, "error requesting fork schedule")
+	}
+	fsr := &forkScheduleResponse{}
+	err = json.Unmarshal(body, fsr)
+	if err != nil {
+		return nil, err
+	}
+	ofs, err := fsr.OrderedForkSchedule()
+	if err != nil {
+		return nil, errors.Wrap(err, fmt.Sprintf("problem unmarshaling %s response", getForkSchedulePath))
+	}
+	return ofs, nil
+}
+
+type NodeVersion struct {
+	implementation string
+	semver         string
+	systemInfo     string
+}
+
+var versionRE = regexp.MustCompile(`^(\w+)\/(v\d+\.\d+\.\d+) \((.*)\)$`)
+
+func parseNodeVersion(v string) (*NodeVersion, error) {
+	groups := versionRE.FindStringSubmatch(v)
+	if len(groups) != 4 {
+		return nil, errors.Wrapf(ErrInvalidNodeVersion, "could not be parsed: %s", v)
+	}
+	return &NodeVersion{
+		implementation: groups[1],
+		semver:         groups[2],
+		systemInfo:     groups[3],
+	}, nil
+}
+
+// GetNodeVersion requests that the beacon node identify information about its implementation in a format
+// similar to a HTTP User-Agent field. ex: Lighthouse/v0.1.5 (Linux x86_64)
+func (c *Client) GetNodeVersion(ctx context.Context) (*NodeVersion, error) {
+	b, err := c.get(ctx, getNodeVersionPath)
+	if err != nil {
+		return nil, errors.Wrap(err, "error requesting node version")
+	}
+	d := struct {
+		Data struct {
+			Version string `json:"version"`
+		} `json:"data"`
+	}{}
+	err = json.Unmarshal(b, &d)
+	if err != nil {
+		return nil, errors.Wrapf(err, "error unmarshaling response body: %s", string(b))
+	}
+	return parseNodeVersion(d.Data.Version)
+}
+
+func renderGetStatePath(id StateOrBlockId) string {
+	return path.Join(getStatePath, string(id))
+}
+
+// GetState retrieves the BeaconState for the given state id.
+// State identifier can be one of: "head" (canonical head in node's view), "genesis", "finalized",
+// <slot>, <hex encoded stateRoot with 0x prefix>. Variables of type StateOrBlockId are exported by this package
+// for the named identifiers.
+// The return value contains the ssz-encoded bytes.
+func (c *Client) GetState(ctx context.Context, stateId StateOrBlockId) ([]byte, error) {
+	statePath := path.Join(getStatePath, string(stateId))
+	b, err := c.get(ctx, statePath, withSSZEncoding())
+	if err != nil {
+		return nil, errors.Wrapf(err, "error requesting state by id = %s", stateId)
+	}
+	return b, nil
+}
+
+// GetWeakSubjectivity calls a proposed API endpoint that is unique to prysm
+// This api method does the following:
+// - computes weak subjectivity epoch
+// - finds the highest non-skipped block preceding the epoch
+// - returns the htr of the found block and returns this + the value of state_root from the block
+func (c *Client) GetWeakSubjectivity(ctx context.Context) (*WeakSubjectivityData, error) {
+	body, err := c.get(ctx, getWeakSubjectivityPath)
+	if err != nil {
+		return nil, err
+	}
+	v := &apimiddleware.WeakSubjectivityResponse{}
+	err = json.Unmarshal(body, v)
+	if err != nil {
+		return nil, err
+	}
+	epoch, err := strconv.ParseUint(v.Data.Checkpoint.Epoch, 10, 64)
+	if err != nil {
+		return nil, err
+	}
+	blockRoot, err := hexutil.Decode(v.Data.Checkpoint.Root)
+	if err != nil {
+		return nil, err
+	}
+	stateRoot, err := hexutil.Decode(v.Data.StateRoot)
+	if err != nil {
+		return nil, err
+	}
+	return &WeakSubjectivityData{
+		Epoch:     types.Epoch(epoch),
+		BlockRoot: bytesutil.ToBytes32(blockRoot),
+		StateRoot: bytesutil.ToBytes32(stateRoot),
+	}, nil
+}
+
+// WeakSubjectivityData represents the state root, block root and epoch of the BeaconState + SignedBeaconBlock
+// that falls at the beginning of the current weak subjectivity period. These values can be used to construct
+// a weak subjectivity checkpoint, or to download a BeaconState+SignedBeaconBlock pair that can be used to bootstrap
+// a new Beacon Node using Checkpoint Sync.
+type WeakSubjectivityData struct {
+	BlockRoot [32]byte
+	StateRoot [32]byte
+	Epoch     types.Epoch
+}
+
+func non200Err(response *http.Response) error {
+	bodyBytes, err := ioutil.ReadAll(response.Body)
+	var body string
+	if err != nil {
+		body = "(Unable to read response body.)"
+	} else {
+		body = "response body:\n" + string(bodyBytes)
+	}
+	msg := fmt.Sprintf("code=%d, url=%s, body=%s", response.StatusCode, response.Request.URL, body)
+	switch response.StatusCode {
+	case 404:
+		return errors.Wrap(ErrNotFound, msg)
+	default:
+		return errors.Wrap(ErrNotOK, msg)
+	}
+}
+
+type forkResponse struct {
+	PreviousVersion string `json:"previous_version"`
+	CurrentVersion  string `json:"current_version"`
+	Epoch           string `json:"epoch"`
+}
+
+func (f *forkResponse) Fork() (*ethpb.Fork, error) {
+	epoch, err := strconv.ParseUint(f.Epoch, 10, 64)
+	if err != nil {
+		return nil, err
+	}
+	cSlice, err := hexutil.Decode(f.CurrentVersion)
+	if err != nil {
+		return nil, err
+	}
+	if len(cSlice) != 4 {
+		return nil, fmt.Errorf("got %d byte version for CurrentVersion, expected 4 bytes. hex=%s", len(cSlice), f.CurrentVersion)
+	}
+	pSlice, err := hexutil.Decode(f.PreviousVersion)
+	if err != nil {
+		return nil, err
+	}
+	if len(pSlice) != 4 {
+		return nil, fmt.Errorf("got %d byte version, expected 4 bytes. version hex=%s", len(pSlice), f.PreviousVersion)
+	}
+	return &ethpb.Fork{
+		CurrentVersion:  cSlice,
+		PreviousVersion: pSlice,
+		Epoch:           types.Epoch(epoch),
+	}, nil
+}
+
+type forkScheduleResponse struct {
+	Data []forkResponse
+}
+
+func (fsr *forkScheduleResponse) OrderedForkSchedule() (forks.OrderedSchedule, error) {
+	ofs := make(forks.OrderedSchedule, 0)
+	for _, d := range fsr.Data {
+		epoch, err := strconv.Atoi(d.Epoch)
+		if err != nil {
+			return nil, err
+		}
+		vSlice, err := hexutil.Decode(d.CurrentVersion)
+		if err != nil {
+			return nil, err
+		}
+		if len(vSlice) != 4 {
+			return nil, fmt.Errorf("got %d byte version, expected 4 bytes. version hex=%s", len(vSlice), d.CurrentVersion)
+		}
+		version := bytesutil.ToBytes4(vSlice)
+		ofs = append(ofs, forks.ForkScheduleEntry{
+			Version: version,
+			Epoch:   types.Epoch(uint64(epoch)),
+		})
+	}
+	sort.Sort(ofs)
+	return ofs, nil
+}
--- a/api/client/beacon/client_test.go
+++ b/api/client/beacon/client_test.go
@@ -0,0 +1,58 @@
+package beacon
+
+import (
+	"testing"
+
+	"github.com/prysmaticlabs/prysm/testing/require"
+)
+
+func TestParseNodeVersion(t *testing.T) {
+	cases := []struct {
+		name string
+		v    string
+		err  error
+		nv   *NodeVersion
+	}{
+		{
+			name: "empty string",
+			v:    "",
+			err:  ErrInvalidNodeVersion,
+		},
+		{
+			name: "Prysm as the version string",
+			v:    "Prysm",
+			err:  ErrInvalidNodeVersion,
+		},
+		{
+			name: "semver only",
+			v:    "v2.0.6",
+			err:  ErrInvalidNodeVersion,
+		},
+		{
+			name: "implementation and semver only",
+			v:    "Prysm/v2.0.6",
+			err:  ErrInvalidNodeVersion,
+		},
+		{
+			name: "complete version",
+			v:    "Prysm/v2.0.6 (linux amd64)",
+			nv: &NodeVersion{
+				implementation: "Prysm",
+				semver:         "v2.0.6",
+				systemInfo:     "linux amd64",
+			},
+		},
+	}
+
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			nv, err := parseNodeVersion(c.v)
+			if c.err != nil {
+				require.ErrorIs(t, err, c.err)
+			} else {
+				require.NoError(t, err)
+				require.DeepEqual(t, c.nv, nv)
+			}
+		})
+	}
+}
--- a/api/client/beacon/doc.go
+++ b/api/client/beacon/doc.go
@@ -0,0 +1,6 @@
+/*
+Package beacon provides a client for interacting with the standard Eth Beacon Node API.
+Interactive swagger documentation for the API is available here: https://ethereum.github.io/beacon-APIs/
+
+*/
+package beacon
--- a/api/client/beacon/errors.go
+++ b/api/client/beacon/errors.go
@@ -0,0 +1,13 @@
+package beacon
+
+import "github.com/pkg/errors"
+
+// ErrNotOK is used to indicate when an HTTP request to the Beacon Node API failed with any non-2xx response code.
+// More specific errors may be returned, but an error in reaction to a non-2xx response will always wrap ErrNotOK.
+var ErrNotOK = errors.New("did not receive 2xx response from API")
+
+// ErrNotFound specifically means that a '404 - NOT FOUND' response was received from the API.
+var ErrNotFound = errors.Wrap(ErrNotOK, "recv 404 NotFound response from API")
+
+// ErrInvalidNodeVersion indicates that the /eth/v1/node/version api response format was not recognized.
+var ErrInvalidNodeVersion = errors.New("invalid node version response")
--- a/api/gateway/BUILD.bazel
+++ b/api/gateway/BUILD.bazel
@@ -5,6 +5,7 @@ go_library(
    srcs = [
        "gateway.go",
        "log.go",
+        "options.go",
    ],
    importpath = "github.com/prysmaticlabs/prysm/api/gateway",
    visibility = [
--- a/api/gateway/apimiddleware/api_middleware.go
+++ b/api/gateway/apimiddleware/api_middleware.go
@@ -3,6 +3,7 @@ package apimiddleware
 import (
 	"net/http"
 	"reflect"
+	"time"

 	"github.com/gorilla/mux"
 )
@@ -14,6 +15,8 @@ import (
 type ApiProxyMiddleware struct {
 	GatewayAddress  string
 	EndpointCreator EndpointFactory
+	Timeout         time.Duration
+	router          *mux.Router
 }

 // EndpointFactory is responsible for creating new instances of Endpoint values.
@@ -29,6 +32,8 @@ type Endpoint struct {
 	GetResponse        interface{}     // The struct corresponding to the JSON structure used in a GET response.
 	PostRequest        interface{}     // The struct corresponding to the JSON structure used in a POST request.
 	PostResponse       interface{}     // The struct corresponding to the JSON structure used in a POST response.
+	DeleteRequest      interface{}     // The struct corresponding to the JSON structure used in a DELETE request.
+	DeleteResponse     interface{}     // The struct corresponding to the JSON structure used in a DELETE response.
 	RequestURLLiterals []string        // Names of URL parameters that should not be base64-encoded.
 	RequestQueryParams []QueryParam    // Query parameters of the request.
 	Err                ErrorJson       // The struct corresponding to the error that should be returned in case of a request failure.
@@ -74,16 +79,23 @@ type fieldProcessor struct {
 // Run starts the proxy, registering all proxy endpoints.
 func (m *ApiProxyMiddleware) Run(gatewayRouter *mux.Router) {
 	for _, path := range m.EndpointCreator.Paths() {
-		m.handleApiPath(gatewayRouter, path, m.EndpointCreator)
+		gatewayRouter.HandleFunc(path, m.WithMiddleware(path))
 	}
+	m.router = gatewayRouter
 }

-func (m *ApiProxyMiddleware) handleApiPath(gatewayRouter *mux.Router, path string, endpointFactory EndpointFactory) {
-	gatewayRouter.HandleFunc(path, func(w http.ResponseWriter, req *http.Request) {
-		endpoint, err := endpointFactory.Create(path)
+// ServeHTTP for the proxy middleware.
+func (m *ApiProxyMiddleware) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+	m.router.ServeHTTP(w, req)
+}
+
+// WithMiddleware wraps the given endpoint handler with the middleware logic.
+func (m *ApiProxyMiddleware) WithMiddleware(path string) http.HandlerFunc {
+	return func(w http.ResponseWriter, req *http.Request) {
+		endpoint, err := m.EndpointCreator.Create(path)
 		if err != nil {
-			errJson := InternalServerErrorWithMessage(err, "could not create endpoint")
-			WriteError(w, errJson, nil)
+			log.WithError(err).Errorf("Could not create endpoint for path: %s", path)
+			return
 		}

 		for _, handler := range endpoint.CustomHandlers {
@@ -93,16 +105,14 @@ func (m *ApiProxyMiddleware) handleApiPath(gatewayRouter *mux.Router, path strin
 		}

 		if req.Method == "POST" {
-			if errJson := deserializeRequestBodyIntoContainerWrapped(endpoint, req, w); errJson != nil {
+			if errJson := handlePostRequestForEndpoint(endpoint, w, req); errJson != nil {
 				WriteError(w, errJson, nil)
 				return
 			}
+		}

-			if errJson := ProcessRequestContainerFields(endpoint.PostRequest); errJson != nil {
-				WriteError(w, errJson, nil)
-				return
-			}
-			if errJson := SetRequestBodyToRequestContainer(endpoint.PostRequest, req); errJson != nil {
+		if req.Method == "DELETE" {
+			if errJson := handleDeleteRequestForEndpoint(endpoint, req); errJson != nil {
 				WriteError(w, errJson, nil)
 				return
 			}
@@ -112,7 +122,7 @@ func (m *ApiProxyMiddleware) handleApiPath(gatewayRouter *mux.Router, path strin
 			WriteError(w, errJson, nil)
 			return
 		}
-		grpcResp, errJson := ProxyRequest(req)
+		grpcResp, errJson := m.ProxyRequest(req)
 		if errJson != nil {
 			WriteError(w, errJson, nil)
 			return
@@ -125,18 +135,20 @@ func (m *ApiProxyMiddleware) handleApiPath(gatewayRouter *mux.Router, path strin

 		var respJson []byte
 		if !GrpcResponseIsEmpty(grpcRespBody) {
-			if errJson := DeserializeGrpcResponseBodyIntoErrorJson(endpoint.Err, grpcRespBody); errJson != nil {
+			respHasError, errJson := HandleGrpcResponseError(endpoint.Err, grpcResp, grpcRespBody, w)
+			if errJson != nil {
 				WriteError(w, errJson, nil)
 				return
 			}
-			if endpoint.Err.Msg() != "" {
-				HandleGrpcResponseError(endpoint.Err, grpcResp, w)
+			if respHasError {
 				return
 			}

 			var resp interface{}
 			if req.Method == "GET" {
 				resp = endpoint.GetResponse
+			} else if req.Method == "DELETE" {
+				resp = endpoint.DeleteResponse
 			} else {
 				resp = endpoint.PostResponse
 			}
@@ -164,7 +176,27 @@ func (m *ApiProxyMiddleware) handleApiPath(gatewayRouter *mux.Router, path strin
 			WriteError(w, errJson, nil)
 			return
 		}
-	})
+	}
+}
+
+func handlePostRequestForEndpoint(endpoint *Endpoint, w http.ResponseWriter, req *http.Request) ErrorJson {
+	if errJson := deserializeRequestBodyIntoContainerWrapped(endpoint, req, w); errJson != nil {
+		return errJson
+	}
+	if errJson := ProcessRequestContainerFields(endpoint.PostRequest); errJson != nil {
+		return errJson
+	}
+	return SetRequestBodyToRequestContainer(endpoint.PostRequest, req)
+}
+
+func handleDeleteRequestForEndpoint(endpoint *Endpoint, req *http.Request) ErrorJson {
+	if errJson := DeserializeRequestBodyIntoContainer(req.Body, endpoint.DeleteRequest); errJson != nil {
+		return errJson
+	}
+	if errJson := ProcessRequestContainerFields(endpoint.DeleteRequest); errJson != nil {
+		return errJson
+	}
+	return SetRequestBodyToRequestContainer(endpoint.DeleteRequest, req)
 }

 func deserializeRequestBodyIntoContainerWrapped(endpoint *Endpoint, req *http.Request, w http.ResponseWriter) ErrorJson {
--- a/api/gateway/apimiddleware/process_request.go
+++ b/api/gateway/apimiddleware/process_request.go
@@ -5,10 +5,10 @@ import (
 	"encoding/json"
 	"io"
 	"io/ioutil"
+	"net"
 	"net/http"
 	"strconv"
 	"strings"
-	"time"

 	"github.com/pkg/errors"
 	"github.com/prysmaticlabs/prysm/api/grpc"
@@ -75,11 +75,14 @@ func (m *ApiProxyMiddleware) PrepareRequestForProxying(endpoint Endpoint, req *h
 }

 // ProxyRequest proxies the request to grpc-gateway.
-func ProxyRequest(req *http.Request) (*http.Response, ErrorJson) {
+func (m *ApiProxyMiddleware) ProxyRequest(req *http.Request) (*http.Response, ErrorJson) {
 	// We do not use http.DefaultClient because it does not have any timeout.
-	netClient := &http.Client{Timeout: time.Minute * 2}
+	netClient := &http.Client{Timeout: m.Timeout}
 	grpcResp, err := netClient.Do(req)
 	if err != nil {
+		if err, ok := err.(net.Error); ok && err.Timeout() {
+			return nil, TimeoutError()
+		}
 		return nil, InternalServerErrorWithMessage(err, "could not proxy request")
 	}
 	if grpcResp == nil {
@@ -97,26 +100,30 @@ func ReadGrpcResponseBody(r io.Reader) ([]byte, ErrorJson) {
 	return body, nil
 }

-// DeserializeGrpcResponseBodyIntoErrorJson deserializes the body from the grpc-gateway's response into an error struct.
-// The struct can be later examined to check if the request resulted in an error.
-func DeserializeGrpcResponseBodyIntoErrorJson(errJson ErrorJson, body []byte) ErrorJson {
-	if err := json.Unmarshal(body, errJson); err != nil {
-		return InternalServerErrorWithMessage(err, "could not unmarshal error")
-	}
-	return nil
-}
-
 // HandleGrpcResponseError acts on an error that resulted from a grpc-gateway's response.
-func HandleGrpcResponseError(errJson ErrorJson, resp *http.Response, w http.ResponseWriter) {
-	// Something went wrong, but the request completed, meaning we can write headers and the error message.
-	for h, vs := range resp.Header {
-		for _, v := range vs {
-			w.Header().Set(h, v)
+func HandleGrpcResponseError(errJson ErrorJson, resp *http.Response, respBody []byte, w http.ResponseWriter) (bool, ErrorJson) {
+	responseHasError := false
+	if err := json.Unmarshal(respBody, errJson); err != nil {
+		return false, InternalServerErrorWithMessage(err, "could not unmarshal error")
+	}
+	if errJson.Msg() != "" {
+		responseHasError = true
+		// Something went wrong, but the request completed, meaning we can write headers and the error message.
+		for h, vs := range resp.Header {
+			for _, v := range vs {
+				w.Header().Set(h, v)
+			}
+		}
+		// Handle gRPC timeout.
+		if resp.StatusCode == http.StatusGatewayTimeout {
+			WriteError(w, TimeoutError(), resp.Header)
+		} else {
+			// Set code to HTTP code because unmarshalled body contained gRPC code.
+			errJson.SetCode(resp.StatusCode)
+			WriteError(w, errJson, resp.Header)
 		}
 	}
-	// Set code to HTTP code because unmarshalled body contained gRPC code.
-	errJson.SetCode(resp.StatusCode)
-	WriteError(w, errJson, resp.Header)
+	return responseHasError, nil
 }

 // GrpcResponseIsEmpty determines whether the grpc-gateway's response body contains no data.
@@ -201,9 +208,11 @@ func WriteMiddlewareResponseHeadersAndBody(grpcResp *http.Response, responseJson
 // WriteError writes the error by manipulating headers and the body of the final response.
 func WriteError(w http.ResponseWriter, errJson ErrorJson, responseHeader http.Header) {
 	// Include custom error in the error JSON.
+	hasCustomError := false
 	if responseHeader != nil {
 		customError, ok := responseHeader["Grpc-Metadata-"+grpc.CustomErrorMetadataKey]
 		if ok {
+			hasCustomError = true
 			// Assume header has only one value and read the 0 index.
 			if err := json.Unmarshal([]byte(customError[0]), errJson); err != nil {
 				log.WithError(err).Error("Could not unmarshal custom error message")
@@ -212,10 +221,29 @@ func WriteError(w http.ResponseWriter, errJson ErrorJson, responseHeader http.He
 		}
 	}

-	j, err := json.Marshal(errJson)
-	if err != nil {
-		log.WithError(err).Error("Could not marshal error message")
-		return
+	var j []byte
+	if hasCustomError {
+		var err error
+		j, err = json.Marshal(errJson)
+		if err != nil {
+			log.WithError(err).Error("Could not marshal error message")
+			return
+		}
+	} else {
+		var err error
+		// We marshal the response body into a DefaultErrorJson if the custom error is not present.
+		// This is because the ErrorJson argument is the endpoint's error definition, which may contain custom fields.
+		// In such a scenario marhaling the endpoint's error would populate the resulting JSON
+		// with these fields even if they are not present in the gRPC header.
+		d := &DefaultErrorJson{
+			Message: errJson.Msg(),
+			Code:    errJson.StatusCode(),
+		}
+		j, err = json.Marshal(d)
+		if err != nil {
+			log.WithError(err).Error("Could not marshal error message")
+			return
+		}
 	}

 	w.Header().Set("Content-Length", strconv.Itoa(len(j)))
--- a/api/gateway/apimiddleware/process_request_test.go
+++ b/api/gateway/apimiddleware/process_request_test.go
@@ -63,6 +63,11 @@ func (e *testErrorJson) SetCode(code int) {
 	e.Code = code
 }

+// SetMsg sets the error's underlying message.
+func (e *testErrorJson) SetMsg(msg string) {
+	e.Message = msg
+}
+
 func TestDeserializeRequestBodyIntoContainer(t *testing.T) {
 	t.Run("ok", func(t *testing.T) {
 		var bodyJson bytes.Buffer
@@ -156,29 +161,6 @@ func TestReadGrpcResponseBody(t *testing.T) {
 	assert.Equal(t, "foo", string(body))
 }

-func TestDeserializeGrpcResponseBodyIntoErrorJson(t *testing.T) {
-	t.Run("ok", func(t *testing.T) {
-		e := &testErrorJson{
-			Message: "foo",
-			Code:    500,
-		}
-		body, err := json.Marshal(e)
-		require.NoError(t, err)
-
-		eToDeserialize := &testErrorJson{}
-		errJson := DeserializeGrpcResponseBodyIntoErrorJson(eToDeserialize, body)
-		require.Equal(t, true, errJson == nil)
-		assert.Equal(t, "foo", eToDeserialize.Msg())
-		assert.Equal(t, 500, eToDeserialize.StatusCode())
-	})
-
-	t.Run("error", func(t *testing.T) {
-		errJson := DeserializeGrpcResponseBodyIntoErrorJson(nil, nil)
-		require.NotNil(t, errJson)
-		assert.Equal(t, true, strings.Contains(errJson.Msg(), "could not unmarshal error"))
-	})
-}
-
 func TestHandleGrpcResponseError(t *testing.T) {
 	response := &http.Response{
 		StatusCode: 400,
@@ -190,10 +172,14 @@ func TestHandleGrpcResponseError(t *testing.T) {
 	writer := httptest.NewRecorder()
 	errJson := &testErrorJson{
 		Message: "foo",
-		Code:    500,
+		Code:    400,
 	}
+	b, err := json.Marshal(errJson)
+	require.NoError(t, err)

-	HandleGrpcResponseError(errJson, response, writer)
+	hasError, e := HandleGrpcResponseError(errJson, response, b, writer)
+	require.Equal(t, true, e == nil)
+	assert.Equal(t, true, hasError)
 	v, ok := writer.Header()["Foo"]
 	require.Equal(t, true, ok, "header not found")
 	require.Equal(t, 1, len(v), "wrong number of header values")
--- a/api/gateway/apimiddleware/structs.go
+++ b/api/gateway/apimiddleware/structs.go
@@ -15,6 +15,7 @@ type ErrorJson interface {
 	StatusCode() int
 	SetCode(code int)
 	Msg() string
+	SetMsg(msg string)
 }

 // DefaultErrorJson is a JSON representation of a simple error value, containing only a message and an error code.
@@ -40,6 +41,13 @@ func InternalServerError(err error) *DefaultErrorJson {
 	}
 }

+func TimeoutError() *DefaultErrorJson {
+	return &DefaultErrorJson{
+		Message: "Request timeout",
+		Code:    http.StatusRequestTimeout,
+	}
+}
+
 // StatusCode returns the error's underlying error code.
 func (e *DefaultErrorJson) StatusCode() int {
 	return e.Code
@@ -54,3 +62,8 @@ func (e *DefaultErrorJson) Msg() string {
 func (e *DefaultErrorJson) SetCode(code int) {
 	e.Code = code
 }
+
+// SetMsg sets the error's underlying message.
+func (e *DefaultErrorJson) SetMsg(msg string) {
+	e.Message = msg
+}
--- a/api/gateway/gateway.go
+++ b/api/gateway/gateway.go
@@ -34,74 +34,52 @@ type PbMux struct {
 type PbHandlerRegistration func(context.Context, *gwruntime.ServeMux, *grpc.ClientConn) error

 // MuxHandler is a function that implements the mux handler functionality.
-type MuxHandler func(http.Handler, http.ResponseWriter, *http.Request)
+type MuxHandler func(
+	apiMiddlewareHandler *apimiddleware.ApiProxyMiddleware,
+	h http.HandlerFunc,
+	w http.ResponseWriter,
+	req *http.Request,
+)
+
+// Config parameters for setting up the gateway service.
+type config struct {
+	maxCallRecvMsgSize           uint64
+	remoteCert                   string
+	gatewayAddr                  string
+	remoteAddr                   string
+	allowedOrigins               []string
+	apiMiddlewareEndpointFactory apimiddleware.EndpointFactory
+	muxHandler                   MuxHandler
+	pbHandlers                   []*PbMux
+	router                       *mux.Router
+	timeout                      time.Duration
+}

 // Gateway is the gRPC gateway to serve HTTP JSON traffic as a proxy and forward it to the gRPC server.
 type Gateway struct {
-	conn                         *grpc.ClientConn
-	pbHandlers                   []*PbMux
-	muxHandler                   MuxHandler
-	maxCallRecvMsgSize           uint64
-	router                       *mux.Router
-	server                       *http.Server
-	cancel                       context.CancelFunc
-	remoteCert                   string
-	gatewayAddr                  string
-	apiMiddlewareEndpointFactory apimiddleware.EndpointFactory
-	ctx                          context.Context
-	startFailure                 error
-	remoteAddr                   string
-	allowedOrigins               []string
+	cfg          *config
+	conn         *grpc.ClientConn
+	server       *http.Server
+	cancel       context.CancelFunc
+	proxy        *apimiddleware.ApiProxyMiddleware
+	ctx          context.Context
+	startFailure error
 }

 // New returns a new instance of the Gateway.
-func New(
-	ctx context.Context,
-	pbHandlers []*PbMux,
-	muxHandler MuxHandler,
-	remoteAddr,
-	gatewayAddress string,
-) *Gateway {
+func New(ctx context.Context, opts ...Option) (*Gateway, error) {
 	g := &Gateway{
-		pbHandlers:     pbHandlers,
-		muxHandler:     muxHandler,
-		router:         mux.NewRouter(),
-		gatewayAddr:    gatewayAddress,
-		ctx:            ctx,
-		remoteAddr:     remoteAddr,
-		allowedOrigins: []string{},
+		ctx: ctx,
+		cfg: &config{
+			router: mux.NewRouter(),
+		},
 	}
-	return g
-}
-
-// WithRouter allows adding a custom mux router to the gateway.
-func (g *Gateway) WithRouter(r *mux.Router) *Gateway {
-	g.router = r
-	return g
-}
-
-// WithAllowedOrigins allows adding a set of allowed origins to the gateway.
-func (g *Gateway) WithAllowedOrigins(origins []string) *Gateway {
-	g.allowedOrigins = origins
-	return g
-}
-
-// WithRemoteCert allows adding a custom certificate to the gateway,
-func (g *Gateway) WithRemoteCert(cert string) *Gateway {
-	g.remoteCert = cert
-	return g
-}
-
-// WithMaxCallRecvMsgSize allows specifying the maximum allowed gRPC message size.
-func (g *Gateway) WithMaxCallRecvMsgSize(size uint64) *Gateway {
-	g.maxCallRecvMsgSize = size
-	return g
-}
-
-// WithApiMiddleware allows adding API Middleware proxy to the gateway.
-func (g *Gateway) WithApiMiddleware(endpointFactory apimiddleware.EndpointFactory) *Gateway {
-	g.apiMiddlewareEndpointFactory = endpointFactory
-	return g
+	for _, opt := range opts {
+		if err := opt(g); err != nil {
+			return nil, err
+		}
+	}
+	return g, nil
 }

 // Start the gateway service.
@@ -109,7 +87,7 @@ func (g *Gateway) Start() {
 	ctx, cancel := context.WithCancel(g.ctx)
 	g.cancel = cancel

-	conn, err := g.dial(ctx, "tcp", g.remoteAddr)
+	conn, err := g.dial(ctx, "tcp", g.cfg.remoteAddr)
 	if err != nil {
 		log.WithError(err).Error("Failed to connect to gRPC server")
 		g.startFailure = err
@@ -117,7 +95,7 @@ func (g *Gateway) Start() {
 	}
 	g.conn = conn

-	for _, h := range g.pbHandlers {
+	for _, h := range g.cfg.pbHandlers {
 		for _, r := range h.Registrations {
 			if err := r(ctx, h.Mux, g.conn); err != nil {
 				log.WithError(err).Error("Failed to register handler")
@@ -126,29 +104,29 @@ func (g *Gateway) Start() {
 			}
 		}
 		for _, p := range h.Patterns {
-			g.router.PathPrefix(p).Handler(h.Mux)
+			g.cfg.router.PathPrefix(p).Handler(h.Mux)
 		}
 	}

-	corsMux := g.corsMiddleware(g.router)
+	corsMux := g.corsMiddleware(g.cfg.router)

-	if g.muxHandler != nil {
-		g.router.PathPrefix("/").HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			g.muxHandler(corsMux, w, r)
+	if g.cfg.apiMiddlewareEndpointFactory != nil && !g.cfg.apiMiddlewareEndpointFactory.IsNil() {
+		g.registerApiMiddleware()
+	}
+
+	if g.cfg.muxHandler != nil {
+		g.cfg.router.PathPrefix("/").HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			g.cfg.muxHandler(g.proxy, corsMux.ServeHTTP, w, r)
 		})
 	}

-	if g.apiMiddlewareEndpointFactory != nil && !g.apiMiddlewareEndpointFactory.IsNil() {
-		go g.registerApiMiddleware()
-	}
-
 	g.server = &http.Server{
-		Addr:    g.gatewayAddr,
-		Handler: g.router,
+		Addr:    g.cfg.gatewayAddr,
+		Handler: corsMux,
 	}

 	go func() {
-		log.WithField("address", g.gatewayAddr).Info("Starting gRPC gateway")
+		log.WithField("address", g.cfg.gatewayAddr).Info("Starting gRPC gateway")
 		if err := g.server.ListenAndServe(); err != http.ErrServerClosed {
 			log.WithError(err).Error("Failed to start gRPC gateway")
 			g.startFailure = err
@@ -162,11 +140,9 @@ func (g *Gateway) Status() error {
 	if g.startFailure != nil {
 		return g.startFailure
 	}
-
 	if s := g.conn.GetState(); s != connectivity.Ready {
 		return fmt.Errorf("grpc server is %s", s)
 	}
-
 	return nil
 }

@@ -183,18 +159,16 @@ func (g *Gateway) Stop() error {
 			}
 		}
 	}
-
 	if g.cancel != nil {
 		g.cancel()
 	}
-
 	return nil
 }

 func (g *Gateway) corsMiddleware(h http.Handler) http.Handler {
 	c := cors.New(cors.Options{
-		AllowedOrigins:   g.allowedOrigins,
-		AllowedMethods:   []string{http.MethodPost, http.MethodGet, http.MethodOptions},
+		AllowedOrigins:   g.cfg.allowedOrigins,
+		AllowedMethods:   []string{http.MethodPost, http.MethodGet, http.MethodDelete, http.MethodOptions},
 		AllowCredentials: true,
 		MaxAge:           600,
 		AllowedHeaders:   []string{"*"},
@@ -236,8 +210,8 @@ func (g *Gateway) dial(ctx context.Context, network, addr string) (*grpc.ClientC
 // "addr" must be a valid TCP address with a port number.
 func (g *Gateway) dialTCP(ctx context.Context, addr string) (*grpc.ClientConn, error) {
 	security := grpc.WithInsecure()
-	if len(g.remoteCert) > 0 {
-		creds, err := credentials.NewClientTLSFromFile(g.remoteCert, "")
+	if len(g.cfg.remoteCert) > 0 {
+		creds, err := credentials.NewClientTLSFromFile(g.cfg.remoteCert, "")
 		if err != nil {
 			return nil, err
 		}
@@ -245,7 +219,7 @@ func (g *Gateway) dialTCP(ctx context.Context, addr string) (*grpc.ClientConn, e
 	}
 	opts := []grpc.DialOption{
 		security,
-		grpc.WithDefaultCallOptions(grpc.MaxCallRecvMsgSize(int(g.maxCallRecvMsgSize))),
+		grpc.WithDefaultCallOptions(grpc.MaxCallRecvMsgSize(int(g.cfg.maxCallRecvMsgSize))),
 	}

 	return grpc.DialContext(ctx, addr, opts...)
@@ -266,16 +240,17 @@ func (g *Gateway) dialUnix(ctx context.Context, addr string) (*grpc.ClientConn,
 	opts := []grpc.DialOption{
 		grpc.WithInsecure(),
 		grpc.WithContextDialer(f),
-		grpc.WithDefaultCallOptions(grpc.MaxCallRecvMsgSize(int(g.maxCallRecvMsgSize))),
+		grpc.WithDefaultCallOptions(grpc.MaxCallRecvMsgSize(int(g.cfg.maxCallRecvMsgSize))),
 	}
 	return grpc.DialContext(ctx, addr, opts...)
 }

 func (g *Gateway) registerApiMiddleware() {
-	proxy := &apimiddleware.ApiProxyMiddleware{
-		GatewayAddress:  g.gatewayAddr,
-		EndpointCreator: g.apiMiddlewareEndpointFactory,
+	g.proxy = &apimiddleware.ApiProxyMiddleware{
+		GatewayAddress:  g.cfg.gatewayAddr,
+		EndpointCreator: g.cfg.apiMiddlewareEndpointFactory,
+		Timeout:         g.cfg.timeout,
 	}
 	log.Info("Starting API middleware")
-	proxy.Run(g.router)
+	g.proxy.Run(g.cfg.router)
 }
--- a/api/gateway/gateway_test.go
+++ b/api/gateway/gateway_test.go
@@ -40,26 +40,30 @@ func TestGateway_Customized(t *testing.T) {
 	size := uint64(100)
 	endpointFactory := &mockEndpointFactory{}

-	g := New(
-		context.Background(),
-		[]*PbMux{},
-		func(handler http.Handler, writer http.ResponseWriter, request *http.Request) {
+	opts := []Option{
+		WithRouter(r),
+		WithRemoteCert(cert),
+		WithAllowedOrigins(origins),
+		WithMaxCallRecvMsgSize(size),
+		WithApiMiddleware(endpointFactory),
+		WithMuxHandler(func(
+			_ *apimiddleware.ApiProxyMiddleware,
+			_ http.HandlerFunc,
+			_ http.ResponseWriter,
+			_ *http.Request,
+		) {
+		}),
+	}

-		},
-		"",
-		"",
-	).WithRouter(r).
-		WithRemoteCert(cert).
-		WithAllowedOrigins(origins).
-		WithMaxCallRecvMsgSize(size).
-		WithApiMiddleware(endpointFactory)
+	g, err := New(context.Background(), opts...)
+	require.NoError(t, err)

-	assert.Equal(t, r, g.router)
-	assert.Equal(t, cert, g.remoteCert)
-	require.Equal(t, 1, len(g.allowedOrigins))
-	assert.Equal(t, origins[0], g.allowedOrigins[0])
-	assert.Equal(t, size, g.maxCallRecvMsgSize)
-	assert.Equal(t, endpointFactory, g.apiMiddlewareEndpointFactory)
+	assert.Equal(t, r, g.cfg.router)
+	assert.Equal(t, cert, g.cfg.remoteCert)
+	require.Equal(t, 1, len(g.cfg.allowedOrigins))
+	assert.Equal(t, origins[0], g.cfg.allowedOrigins[0])
+	assert.Equal(t, size, g.cfg.maxCallRecvMsgSize)
+	assert.Equal(t, endpointFactory, g.cfg.apiMiddlewareEndpointFactory)
 }

 func TestGateway_StartStop(t *testing.T) {
@@ -75,23 +79,27 @@ func TestGateway_StartStop(t *testing.T) {
 	selfAddress := fmt.Sprintf("%s:%d", rpcHost, ctx.Int(flags.RPCPort.Name))
 	gatewayAddress := fmt.Sprintf("%s:%d", gatewayHost, gatewayPort)

-	g := New(
-		ctx.Context,
-		[]*PbMux{},
-		func(handler http.Handler, writer http.ResponseWriter, request *http.Request) {
+	opts := []Option{
+		WithGatewayAddr(gatewayAddress),
+		WithRemoteAddr(selfAddress),
+		WithMuxHandler(func(
+			_ *apimiddleware.ApiProxyMiddleware,
+			_ http.HandlerFunc,
+			_ http.ResponseWriter,
+			_ *http.Request,
+		) {
+		}),
+	}

-		},
-		selfAddress,
-		gatewayAddress,
-	)
+	g, err := New(context.Background(), opts...)
+	require.NoError(t, err)

 	g.Start()
 	go func() {
 		require.LogsContain(t, hook, "Starting gRPC gateway")
 		require.LogsDoNotContain(t, hook, "Starting API middleware")
 	}()
-
-	err := g.Stop()
+	err = g.Stop()
 	require.NoError(t, err)
 }

@@ -106,15 +114,15 @@ func TestGateway_NilHandler_NotFoundHandlerRegistered(t *testing.T) {
 	selfAddress := fmt.Sprintf("%s:%d", rpcHost, ctx.Int(flags.RPCPort.Name))
 	gatewayAddress := fmt.Sprintf("%s:%d", gatewayHost, gatewayPort)

-	g := New(
-		ctx.Context,
-		[]*PbMux{},
-		/* muxHandler */ nil,
-		selfAddress,
-		gatewayAddress,
-	)
+	opts := []Option{
+		WithGatewayAddr(gatewayAddress),
+		WithRemoteAddr(selfAddress),
+	}
+
+	g, err := New(context.Background(), opts...)
+	require.NoError(t, err)

 	writer := httptest.NewRecorder()
-	g.router.ServeHTTP(writer, &http.Request{Method: "GET", Host: "localhost", URL: &url.URL{Path: "/foo"}})
+	g.cfg.router.ServeHTTP(writer, &http.Request{Method: "GET", Host: "localhost", URL: &url.URL{Path: "/foo"}})
 	assert.Equal(t, http.StatusNotFound, writer.Code)
 }
--- a/api/gateway/options.go
+++ b/api/gateway/options.go
@@ -0,0 +1,93 @@
+package gateway
+
+import (
+	"time"
+
+	"github.com/gorilla/mux"
+	gwruntime "github.com/grpc-ecosystem/grpc-gateway/v2/runtime"
+	"github.com/prysmaticlabs/prysm/api/gateway/apimiddleware"
+)
+
+type Option func(g *Gateway) error
+
+func (g *Gateway) SetRouter(r *mux.Router) *Gateway {
+	g.cfg.router = r
+	return g
+}
+
+func WithPbHandlers(handlers []*PbMux) Option {
+	return func(g *Gateway) error {
+		g.cfg.pbHandlers = handlers
+		return nil
+	}
+}
+
+func WithMuxHandler(m MuxHandler) Option {
+	return func(g *Gateway) error {
+		g.cfg.muxHandler = m
+		return nil
+	}
+}
+
+func WithGatewayAddr(addr string) Option {
+	return func(g *Gateway) error {
+		g.cfg.gatewayAddr = addr
+		return nil
+	}
+}
+
+func WithRemoteAddr(addr string) Option {
+	return func(g *Gateway) error {
+		g.cfg.remoteAddr = addr
+		return nil
+	}
+}
+
+// WithRouter allows adding a custom mux router to the gateway.
+func WithRouter(r *mux.Router) Option {
+	return func(g *Gateway) error {
+		g.cfg.router = r
+		return nil
+	}
+}
+
+// WithAllowedOrigins allows adding a set of allowed origins to the gateway.
+func WithAllowedOrigins(origins []string) Option {
+	return func(g *Gateway) error {
+		g.cfg.allowedOrigins = origins
+		return nil
+	}
+}
+
+// WithRemoteCert allows adding a custom certificate to the gateway,
+func WithRemoteCert(cert string) Option {
+	return func(g *Gateway) error {
+		g.cfg.remoteCert = cert
+		return nil
+	}
+}
+
+// WithMaxCallRecvMsgSize allows specifying the maximum allowed gRPC message size.
+func WithMaxCallRecvMsgSize(size uint64) Option {
+	return func(g *Gateway) error {
+		g.cfg.maxCallRecvMsgSize = size
+		return nil
+	}
+}
+
+// WithApiMiddleware allows adding an API middleware proxy to the gateway.
+func WithApiMiddleware(endpointFactory apimiddleware.EndpointFactory) Option {
+	return func(g *Gateway) error {
+		g.cfg.apiMiddlewareEndpointFactory = endpointFactory
+		return nil
+	}
+}
+
+// WithTimeout allows changing the timeout value for API calls.
+func WithTimeout(seconds uint64) Option {
+	return func(g *Gateway) error {
+		g.cfg.timeout = time.Second * time.Duration(seconds)
+		gwruntime.DefaultContextTimeout = time.Second * time.Duration(seconds)
+		return nil
+	}
+}
--- a/async/multilock_test.go
+++ b/async/multilock_test.go
@@ -110,9 +110,8 @@ func TestLockUnlock_CleansUnused(t *testing.T) {
 		lock := NewMultilock("dog", "cat", "owl")
 		lock.Lock()
 		assert.Equal(t, 3, len(locks.list))
-		defer lock.Unlock()
+		lock.Unlock()

-		<-time.After(100 * time.Millisecond)
 		wg.Done()
 	}()
 	wg.Wait()
--- a/beacon-chain/blockchain/BUILD.bazel
+++ b/beacon-chain/blockchain/BUILD.bazel
@@ -4,12 +4,16 @@ go_library(
    name = "go_default_library",
    srcs = [
        "chain_info.go",
+        "error.go",
        "head.go",
        "head_sync_committee_info.go",
-        "info.go",
        "init_sync_process_block.go",
        "log.go",
        "metrics.go",
+        "new_slot.go",
+        "optimistic_sync.go",
+        "options.go",
+        "pow_block.go",
        "process_attestation.go",
        "process_attestation_helpers.go",
        "process_block.go",
@@ -17,20 +21,24 @@ go_library(
        "receive_attestation.go",
        "receive_block.go",
        "service.go",
+        "state_balance_cache.go",
        "weak_subjectivity_checks.go",
    ],
    importpath = "github.com/prysmaticlabs/prysm/beacon-chain/blockchain",
    visibility = [
        "//beacon-chain:__subpackages__",
-        "//testing/fuzz:__pkg__",
+        "//cmd/beacon-chain:__subpackages__",
        "//testing/slasher/simulator:__pkg__",
+        "//testing/spectest:__subpackages__",
    ],
    deps = [
        "//async:go_default_library",
        "//async/event:go_default_library",
+        "//beacon-chain/blockchain/store:go_default_library",
        "//beacon-chain/cache:go_default_library",
        "//beacon-chain/cache/depositcache:go_default_library",
        "//beacon-chain/core/altair:go_default_library",
+        "//beacon-chain/core/blocks:go_default_library",
        "//beacon-chain/core/epoch/precompute:go_default_library",
        "//beacon-chain/core/feed:go_default_library",
        "//beacon-chain/core/feed/state:go_default_library",
@@ -41,20 +49,25 @@ go_library(
        "//beacon-chain/db:go_default_library",
        "//beacon-chain/db/filters:go_default_library",
        "//beacon-chain/forkchoice:go_default_library",
+        "//beacon-chain/forkchoice/doubly-linked-tree:go_default_library",
        "//beacon-chain/forkchoice/protoarray:go_default_library",
+        "//beacon-chain/forkchoice/types:go_default_library",
        "//beacon-chain/operations/attestations:go_default_library",
        "//beacon-chain/operations/slashings:go_default_library",
        "//beacon-chain/operations/voluntaryexits:go_default_library",
        "//beacon-chain/p2p:go_default_library",
        "//beacon-chain/powchain:go_default_library",
+        "//beacon-chain/powchain/engine-api-client/v1:go_default_library",
        "//beacon-chain/state:go_default_library",
        "//beacon-chain/state/stategen:go_default_library",
        "//cmd/beacon-chain/flags:go_default_library",
        "//config/features:go_default_library",
+        "//config/fieldparams:go_default_library",
        "//config/params:go_default_library",
        "//crypto/bls:go_default_library",
        "//encoding/bytesutil:go_default_library",
        "//monitoring/tracing:go_default_library",
+        "//proto/engine/v1:go_default_library",
        "//proto/eth/v1:go_default_library",
        "//proto/prysm/v1alpha1:go_default_library",
        "//proto/prysm/v1alpha1/attestation:go_default_library",
@@ -62,7 +75,9 @@ go_library(
        "//runtime/version:go_default_library",
        "//time:go_default_library",
        "//time/slots:go_default_library",
-        "@com_github_emicklei_dot//:go_default_library",
+        "@com_github_ethereum_go_ethereum//common:go_default_library",
+        "@com_github_ethereum_go_ethereum//common/hexutil:go_default_library",
+        "@com_github_holiman_uint256//:go_default_library",
        "@com_github_pkg_errors//:go_default_library",
        "@com_github_prometheus_client_golang//prometheus:go_default_library",
        "@com_github_prometheus_client_golang//prometheus/promauto:go_default_library",
@@ -89,10 +104,13 @@ go_test(
        "checktags_test.go",
        "head_sync_committee_info_test.go",
        "head_test.go",
-        "info_test.go",
        "init_test.go",
        "log_test.go",
        "metrics_test.go",
+        "mock_engine_test.go",
+        "mock_test.go",
+        "optimistic_sync_test.go",
+        "pow_block_test.go",
        "process_attestation_test.go",
        "process_block_test.go",
        "receive_attestation_test.go",
@@ -115,6 +133,7 @@ go_test(
        "//beacon-chain/powchain:go_default_library",
        "//beacon-chain/state/stateutil:go_default_library",
        "//beacon-chain/state/v1:go_default_library",
+        "//config/fieldparams:go_default_library",
        "//config/params:go_default_library",
        "//encoding/bytesutil:go_default_library",
        "//proto/prysm/v1alpha1:go_default_library",
@@ -139,6 +158,7 @@ go_test(
        "chain_info_norace_test.go",
        "checktags_test.go",
        "init_test.go",
+        "mock_test.go",
        "receive_block_test.go",
        "service_norace_test.go",
    ],
--- a/beacon-chain/blockchain/chain_info.go
+++ b/beacon-chain/blockchain/chain_info.go
@@ -6,12 +6,16 @@ import (

 	types "github.com/prysmaticlabs/eth2-types"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
+	"github.com/prysmaticlabs/prysm/beacon-chain/forkchoice"
+	doublylinkedtree "github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/doubly-linked-tree"
 	"github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/protoarray"
 	"github.com/prysmaticlabs/prysm/beacon-chain/state"
+	fieldparams "github.com/prysmaticlabs/prysm/config/fieldparams"
 	"github.com/prysmaticlabs/prysm/config/params"
 	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
 	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
 	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/block"
+	"github.com/prysmaticlabs/prysm/time/slots"
 	"go.opencensus.io/trace"
 )

@@ -35,7 +39,7 @@ type TimeFetcher interface {

 // GenesisFetcher retrieves the Ethereum consensus data related to its genesis.
 type GenesisFetcher interface {
-	GenesisValidatorRoot() [32]byte
+	GenesisValidatorsRoot() [32]byte
 }

 // HeadFetcher defines a common interface for methods in blockchain service which
@@ -47,14 +51,16 @@ type HeadFetcher interface {
 	HeadState(ctx context.Context) (state.BeaconState, error)
 	HeadValidatorsIndices(ctx context.Context, epoch types.Epoch) ([]types.ValidatorIndex, error)
 	HeadSeed(ctx context.Context, epoch types.Epoch) ([32]byte, error)
-	HeadGenesisValidatorRoot() [32]byte
+	HeadGenesisValidatorsRoot() [32]byte
 	HeadETH1Data() *ethpb.Eth1Data
-	HeadPublicKeyToValidatorIndex(ctx context.Context, pubKey [48]byte) (types.ValidatorIndex, bool)
-	HeadValidatorIndexToPublicKey(ctx context.Context, index types.ValidatorIndex) ([48]byte, error)
-	ProtoArrayStore() *protoarray.Store
+	HeadPublicKeyToValidatorIndex(pubKey [fieldparams.BLSPubkeyLength]byte) (types.ValidatorIndex, bool)
+	HeadValidatorIndexToPublicKey(ctx context.Context, index types.ValidatorIndex) ([fieldparams.BLSPubkeyLength]byte, error)
 	ChainHeads() ([][32]byte, []types.Slot)
+	IsOptimistic(ctx context.Context) (bool, error)
+	IsOptimisticForRoot(ctx context.Context, root [32]byte) (bool, error)
 	HeadSyncCommitteeFetcher
 	HeadDomainFetcher
+	ForkChoicer() forkchoice.ForkChoicer
 }

 // ForkFetcher retrieves the current fork information of the Ethereum beacon chain.
@@ -76,31 +82,45 @@ type FinalizationFetcher interface {
 	PreviousJustifiedCheckpt() *ethpb.Checkpoint
 }

-// FinalizedCheckpt returns the latest finalized checkpoint from head state.
+// FinalizedCheckpt returns the latest finalized checkpoint from chain store.
 func (s *Service) FinalizedCheckpt() *ethpb.Checkpoint {
-	if s.finalizedCheckpt == nil {
+	cp := s.store.FinalizedCheckpt()
+	if cp == nil {
 		return &ethpb.Checkpoint{Root: params.BeaconConfig().ZeroHash[:]}
 	}

-	return ethpb.CopyCheckpoint(s.finalizedCheckpt)
+	return ethpb.CopyCheckpoint(cp)
 }

-// CurrentJustifiedCheckpt returns the current justified checkpoint from head state.
+// CurrentJustifiedCheckpt returns the current justified checkpoint from chain store.
 func (s *Service) CurrentJustifiedCheckpt() *ethpb.Checkpoint {
-	if s.justifiedCheckpt == nil {
+	cp := s.store.JustifiedCheckpt()
+	if cp == nil {
 		return &ethpb.Checkpoint{Root: params.BeaconConfig().ZeroHash[:]}
 	}

-	return ethpb.CopyCheckpoint(s.justifiedCheckpt)
+	return ethpb.CopyCheckpoint(cp)
 }

-// PreviousJustifiedCheckpt returns the previous justified checkpoint from head state.
+// PreviousJustifiedCheckpt returns the previous justified checkpoint from chain store.
 func (s *Service) PreviousJustifiedCheckpt() *ethpb.Checkpoint {
-	if s.prevJustifiedCheckpt == nil {
+	cp := s.store.PrevJustifiedCheckpt()
+	if cp == nil {
 		return &ethpb.Checkpoint{Root: params.BeaconConfig().ZeroHash[:]}
 	}

-	return ethpb.CopyCheckpoint(s.prevJustifiedCheckpt)
+	return ethpb.CopyCheckpoint(cp)
+}
+
+// BestJustifiedCheckpt returns the best justified checkpoint from store.
+func (s *Service) BestJustifiedCheckpt() *ethpb.Checkpoint {
+	cp := s.store.BestJustifiedCheckpt()
+	// If there is no best justified checkpoint, return the checkpoint with root as zeros to be used for genesis cases.
+	if cp == nil {
+		return &ethpb.Checkpoint{Root: params.BeaconConfig().ZeroHash[:]}
+	}
+
+	return ethpb.CopyCheckpoint(cp)
 }

 // HeadSlot returns the slot of the head of the chain.
@@ -197,8 +217,8 @@ func (s *Service) HeadSeed(ctx context.Context, epoch types.Epoch) ([32]byte, er
 	return helpers.Seed(s.headState(ctx), epoch, params.BeaconConfig().DomainBeaconAttester)
 }

-// HeadGenesisValidatorRoot returns genesis validator root of the head state.
-func (s *Service) HeadGenesisValidatorRoot() [32]byte {
+// HeadGenesisValidatorsRoot returns genesis validators root of the head state.
+func (s *Service) HeadGenesisValidatorsRoot() [32]byte {
 	s.headLock.RLock()
 	defer s.headLock.RUnlock()

@@ -206,7 +226,7 @@ func (s *Service) HeadGenesisValidatorRoot() [32]byte {
 		return [32]byte{}
 	}

-	return s.headGenesisValidatorRoot()
+	return s.headGenesisValidatorsRoot()
 }

 // HeadETH1Data returns the eth1data of the current head state.
@@ -220,26 +240,21 @@ func (s *Service) HeadETH1Data() *ethpb.Eth1Data {
 	return s.head.state.Eth1Data()
 }

-// ProtoArrayStore returns the proto array store object.
-func (s *Service) ProtoArrayStore() *protoarray.Store {
-	return s.cfg.ForkChoiceStore.Store()
-}
-
 // GenesisTime returns the genesis time of beacon chain.
 func (s *Service) GenesisTime() time.Time {
 	return s.genesisTime
 }

-// GenesisValidatorRoot returns the genesis validator
+// GenesisValidatorsRoot returns the genesis validator
 // root of the chain.
-func (s *Service) GenesisValidatorRoot() [32]byte {
+func (s *Service) GenesisValidatorsRoot() [32]byte {
 	s.headLock.RLock()
 	defer s.headLock.RUnlock()

 	if !s.hasHeadState() {
 		return [32]byte{}
 	}
-	return bytesutil.ToBytes32(s.head.state.GenesisValidatorRoot())
+	return bytesutil.ToBytes32(s.head.state.GenesisValidatorsRoot())
 }

 // CurrentFork retrieves the latest fork information of the beacon chain.
@@ -270,45 +285,92 @@ func (s *Service) IsCanonical(ctx context.Context, blockRoot [32]byte) (bool, er
 // ChainHeads returns all possible chain heads (leaves of fork choice tree).
 // Heads roots and heads slots are returned.
 func (s *Service) ChainHeads() ([][32]byte, []types.Slot) {
-	nodes := s.ProtoArrayStore().Nodes()
-
-	// Deliberate choice to not preallocate space for below.
-	// Heads cant be more than 2-3 in the worst case where pre-allocation will be 64 to begin with.
-	headsRoots := make([][32]byte, 0)
-	headsSlots := make([]types.Slot, 0)
-
-	nonExistentNode := ^uint64(0)
-	for _, node := range nodes {
-		// Possible heads have no children.
-		if node.BestDescendant() == nonExistentNode && node.BestChild() == nonExistentNode {
-			headsRoots = append(headsRoots, node.Root())
-			headsSlots = append(headsSlots, node.Slot())
-		}
-	}
-
-	return headsRoots, headsSlots
+	return s.cfg.ForkChoiceStore.Tips()
 }

 // HeadPublicKeyToValidatorIndex returns the validator index of the `pubkey` in current head state.
-func (s *Service) HeadPublicKeyToValidatorIndex(ctx context.Context, pubKey [48]byte) (types.ValidatorIndex, bool) {
+func (s *Service) HeadPublicKeyToValidatorIndex(pubKey [fieldparams.BLSPubkeyLength]byte) (types.ValidatorIndex, bool) {
 	s.headLock.RLock()
 	defer s.headLock.RUnlock()
 	if !s.hasHeadState() {
 		return 0, false
 	}
-	return s.headState(ctx).ValidatorIndexByPubkey(pubKey)
+	return s.headValidatorIndexAtPubkey(pubKey)
 }

 // HeadValidatorIndexToPublicKey returns the pubkey of the validator `index`  in current head state.
-func (s *Service) HeadValidatorIndexToPublicKey(_ context.Context, index types.ValidatorIndex) ([48]byte, error) {
+func (s *Service) HeadValidatorIndexToPublicKey(_ context.Context, index types.ValidatorIndex) ([fieldparams.BLSPubkeyLength]byte, error) {
 	s.headLock.RLock()
 	defer s.headLock.RUnlock()
 	if !s.hasHeadState() {
-		return [48]byte{}, nil
+		return [fieldparams.BLSPubkeyLength]byte{}, nil
 	}
 	v, err := s.headValidatorAtIndex(index)
 	if err != nil {
-		return [48]byte{}, err
+		return [fieldparams.BLSPubkeyLength]byte{}, err
 	}
 	return v.PublicKey(), nil
 }
+
+// ForkChoicer returns the forkchoice interface
+func (s *Service) ForkChoicer() forkchoice.ForkChoicer {
+	return s.cfg.ForkChoiceStore
+}
+
+// IsOptimistic returns true if the current head is optimistic.
+func (s *Service) IsOptimistic(ctx context.Context) (bool, error) {
+	s.headLock.RLock()
+	defer s.headLock.RUnlock()
+	if slots.ToEpoch(s.CurrentSlot()) < params.BeaconConfig().BellatrixForkEpoch {
+		return false, nil
+	}
+
+	return s.IsOptimisticForRoot(ctx, s.head.root)
+}
+
+// IsOptimisticForRoot takes the root and slot as aguments instead of the current head
+// and returns true if it is optimistic.
+func (s *Service) IsOptimisticForRoot(ctx context.Context, root [32]byte) (bool, error) {
+	optimistic, err := s.cfg.ForkChoiceStore.IsOptimistic(ctx, root)
+	if err == nil {
+		return optimistic, nil
+	}
+	if err != protoarray.ErrUnknownNodeRoot && err != doublylinkedtree.ErrNilNode {
+		return false, err
+	}
+	ss, err := s.cfg.BeaconDB.StateSummary(ctx, root)
+	if err != nil {
+		return false, err
+	}
+	if ss == nil {
+		return false, errInvalidNilSummary
+	}
+
+	validatedCheckpoint, err := s.cfg.BeaconDB.LastValidatedCheckpoint(ctx)
+	if err != nil {
+		return false, err
+	}
+	if slots.ToEpoch(ss.Slot) > validatedCheckpoint.Epoch {
+		return true, nil
+	}
+
+	if slots.ToEpoch(ss.Slot)+1 < validatedCheckpoint.Epoch {
+		return false, nil
+	}
+
+	lastValidated, err := s.cfg.BeaconDB.StateSummary(ctx, bytesutil.ToBytes32(validatedCheckpoint.Root))
+	if err != nil {
+		return false, err
+	}
+	return ss.Slot > lastValidated.Slot, nil
+}
+
+// SetGenesisTime sets the genesis time of beacon chain.
+func (s *Service) SetGenesisTime(t time.Time) {
+	s.genesisTime = t
+}
+
+// ForkChoiceStore returns the fork choice store in the service
+func (s *Service) ForkChoiceStore() forkchoice.ForkChoicer {
+	return s.cfg.ForkChoiceStore
+}
--- a/beacon-chain/blockchain/chain_info_norace_test.go
+++ b/beacon-chain/blockchain/chain_info_norace_test.go
@@ -14,48 +14,62 @@ import (
 func TestHeadSlot_DataRace(t *testing.T) {
 	beaconDB := testDB.SetupDB(t)
 	s := &Service{
-		cfg: &Config{BeaconDB: beaconDB},
+		cfg: &config{BeaconDB: beaconDB},
 	}
+	wait := make(chan struct{})
 	go func() {
+		defer close(wait)
 		require.NoError(t, s.saveHead(context.Background(), [32]byte{}))
 	}()
 	s.HeadSlot()
+	<-wait
 }

 func TestHeadRoot_DataRace(t *testing.T) {
 	beaconDB := testDB.SetupDB(t)
 	s := &Service{
-		cfg:  &Config{BeaconDB: beaconDB, StateGen: stategen.New(beaconDB)},
+		cfg:  &config{BeaconDB: beaconDB, StateGen: stategen.New(beaconDB)},
 		head: &head{root: [32]byte{'A'}},
 	}
+	wait := make(chan struct{})
 	go func() {
+		defer close(wait)
 		require.NoError(t, s.saveHead(context.Background(), [32]byte{}))
 	}()
 	_, err := s.HeadRoot(context.Background())
 	require.NoError(t, err)
+	<-wait
 }

 func TestHeadBlock_DataRace(t *testing.T) {
 	beaconDB := testDB.SetupDB(t)
+	wsb, err := wrapper.WrappedSignedBeaconBlock(&ethpb.SignedBeaconBlock{})
+	require.NoError(t, err)
 	s := &Service{
-		cfg:  &Config{BeaconDB: beaconDB, StateGen: stategen.New(beaconDB)},
-		head: &head{block: wrapper.WrappedPhase0SignedBeaconBlock(&ethpb.SignedBeaconBlock{})},
+		cfg:  &config{BeaconDB: beaconDB, StateGen: stategen.New(beaconDB)},
+		head: &head{block: wsb},
 	}
+	wait := make(chan struct{})
 	go func() {
+		defer close(wait)
 		require.NoError(t, s.saveHead(context.Background(), [32]byte{}))
 	}()
-	_, err := s.HeadBlock(context.Background())
+	_, err = s.HeadBlock(context.Background())
 	require.NoError(t, err)
+	<-wait
 }

 func TestHeadState_DataRace(t *testing.T) {
 	beaconDB := testDB.SetupDB(t)
 	s := &Service{
-		cfg: &Config{BeaconDB: beaconDB, StateGen: stategen.New(beaconDB)},
+		cfg: &config{BeaconDB: beaconDB, StateGen: stategen.New(beaconDB)},
 	}
+	wait := make(chan struct{})
 	go func() {
+		defer close(wait)
 		require.NoError(t, s.saveHead(context.Background(), [32]byte{}))
 	}()
 	_, err := s.HeadState(context.Background())
 	require.NoError(t, err)
+	<-wait
 }
--- a/beacon-chain/blockchain/chain_info_test.go
+++ b/beacon-chain/blockchain/chain_info_test.go
@@ -8,8 +8,10 @@ import (
 	types "github.com/prysmaticlabs/eth2-types"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
 	testDB "github.com/prysmaticlabs/prysm/beacon-chain/db/testing"
+	doublylinkedtree "github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/doubly-linked-tree"
 	"github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/protoarray"
 	v1 "github.com/prysmaticlabs/prysm/beacon-chain/state/v1"
+	fieldparams "github.com/prysmaticlabs/prysm/config/fieldparams"
 	"github.com/prysmaticlabs/prysm/config/params"
 	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
 	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
@@ -39,12 +41,18 @@ func TestHeadRoot_Nil(t *testing.T) {
 	assert.DeepEqual(t, params.BeaconConfig().ZeroHash[:], headRoot, "Incorrect pre chain start value")
 }

+func TestService_ForkChoiceStore(t *testing.T) {
+	c := &Service{cfg: &config{ForkChoiceStore: doublylinkedtree.New(0, 0)}}
+	p := c.ForkChoiceStore()
+	require.Equal(t, 0, int(p.FinalizedEpoch()))
+}
+
 func TestFinalizedCheckpt_CanRetrieve(t *testing.T) {
 	beaconDB := testDB.SetupDB(t)

 	cp := &ethpb.Checkpoint{Epoch: 5, Root: bytesutil.PadTo([]byte("foo"), 32)}
 	c := setupBeaconChain(t, beaconDB)
-	c.finalizedCheckpt = cp
+	c.store.SetFinalizedCheckpt(cp)

 	assert.Equal(t, cp.Epoch, c.FinalizedCheckpt().Epoch, "Unexpected finalized epoch")
 }
@@ -55,9 +63,9 @@ func TestFinalizedCheckpt_GenesisRootOk(t *testing.T) {
 	genesisRoot := [32]byte{'A'}
 	cp := &ethpb.Checkpoint{Root: genesisRoot[:]}
 	c := setupBeaconChain(t, beaconDB)
-	c.finalizedCheckpt = cp
-	c.genesisRoot = genesisRoot
-	assert.DeepEqual(t, c.genesisRoot[:], c.FinalizedCheckpt().Root)
+	c.store.SetFinalizedCheckpt(cp)
+	c.originBlockRoot = genesisRoot
+	assert.DeepEqual(t, c.originBlockRoot[:], c.FinalizedCheckpt().Root)
 }

 func TestCurrentJustifiedCheckpt_CanRetrieve(t *testing.T) {
@@ -66,7 +74,7 @@ func TestCurrentJustifiedCheckpt_CanRetrieve(t *testing.T) {
 	c := setupBeaconChain(t, beaconDB)
 	assert.Equal(t, params.BeaconConfig().ZeroHash, bytesutil.ToBytes32(c.CurrentJustifiedCheckpt().Root), "Unexpected justified epoch")
 	cp := &ethpb.Checkpoint{Epoch: 6, Root: bytesutil.PadTo([]byte("foo"), 32)}
-	c.justifiedCheckpt = cp
+	c.store.SetJustifiedCheckpt(cp)
 	assert.Equal(t, cp.Epoch, c.CurrentJustifiedCheckpt().Epoch, "Unexpected justified epoch")
 }

@@ -76,9 +84,9 @@ func TestJustifiedCheckpt_GenesisRootOk(t *testing.T) {
 	c := setupBeaconChain(t, beaconDB)
 	genesisRoot := [32]byte{'B'}
 	cp := &ethpb.Checkpoint{Root: genesisRoot[:]}
-	c.justifiedCheckpt = cp
-	c.genesisRoot = genesisRoot
-	assert.DeepEqual(t, c.genesisRoot[:], c.CurrentJustifiedCheckpt().Root)
+	c.store.SetJustifiedCheckpt(cp)
+	c.originBlockRoot = genesisRoot
+	assert.DeepEqual(t, c.originBlockRoot[:], c.CurrentJustifiedCheckpt().Root)
 }

 func TestPreviousJustifiedCheckpt_CanRetrieve(t *testing.T) {
@@ -87,7 +95,7 @@ func TestPreviousJustifiedCheckpt_CanRetrieve(t *testing.T) {
 	cp := &ethpb.Checkpoint{Epoch: 7, Root: bytesutil.PadTo([]byte("foo"), 32)}
 	c := setupBeaconChain(t, beaconDB)
 	assert.Equal(t, params.BeaconConfig().ZeroHash, bytesutil.ToBytes32(c.CurrentJustifiedCheckpt().Root), "Unexpected justified epoch")
-	c.prevJustifiedCheckpt = cp
+	c.store.SetPrevJustifiedCheckpt(cp)
 	assert.Equal(t, cp.Epoch, c.PreviousJustifiedCheckpt().Epoch, "Unexpected previous justified epoch")
 }

@@ -97,9 +105,9 @@ func TestPrevJustifiedCheckpt_GenesisRootOk(t *testing.T) {
 	genesisRoot := [32]byte{'C'}
 	cp := &ethpb.Checkpoint{Root: genesisRoot[:]}
 	c := setupBeaconChain(t, beaconDB)
-	c.prevJustifiedCheckpt = cp
-	c.genesisRoot = genesisRoot
-	assert.DeepEqual(t, c.genesisRoot[:], c.PreviousJustifiedCheckpt().Root)
+	c.store.SetPrevJustifiedCheckpt(cp)
+	c.originBlockRoot = genesisRoot
+	assert.DeepEqual(t, c.originBlockRoot[:], c.PreviousJustifiedCheckpt().Root)
 }

 func TestHeadSlot_CanRetrieve(t *testing.T) {
@@ -120,12 +128,14 @@ func TestHeadRoot_CanRetrieve(t *testing.T) {

 func TestHeadRoot_UseDB(t *testing.T) {
 	beaconDB := testDB.SetupDB(t)
-	c := &Service{cfg: &Config{BeaconDB: beaconDB}}
+	c := &Service{cfg: &config{BeaconDB: beaconDB}}
 	c.head = &head{root: params.BeaconConfig().ZeroHash}
 	b := util.NewBeaconBlock()
 	br, err := b.Block.HashTreeRoot()
 	require.NoError(t, err)
-	require.NoError(t, beaconDB.SaveBlock(context.Background(), wrapper.WrappedPhase0SignedBeaconBlock(b)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(b)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(context.Background(), wsb))
 	require.NoError(t, beaconDB.SaveStateSummary(context.Background(), &ethpb.StateSummary{Root: br[:]}))
 	require.NoError(t, beaconDB.SaveHeadBlockRoot(context.Background(), br))
 	r, err := c.HeadRoot(context.Background())
@@ -138,8 +148,10 @@ func TestHeadBlock_CanRetrieve(t *testing.T) {
 	b.Block.Slot = 1
 	s, err := v1.InitializeFromProto(&ethpb.BeaconState{})
 	require.NoError(t, err)
+	wsb, err := wrapper.WrappedSignedBeaconBlock(b)
+	require.NoError(t, err)
 	c := &Service{}
-	c.head = &head{block: wrapper.WrappedPhase0SignedBeaconBlock(b), state: s}
+	c.head = &head{block: wsb, state: s}

 	recevied, err := c.HeadBlock(context.Background())
 	require.NoError(t, err)
@@ -184,15 +196,15 @@ func TestCurrentFork_NilHeadSTate(t *testing.T) {
 	}
 }

-func TestGenesisValidatorRoot_CanRetrieve(t *testing.T) {
+func TestGenesisValidatorsRoot_CanRetrieve(t *testing.T) {
 	// Should not panic if head state is nil.
 	c := &Service{}
-	assert.Equal(t, [32]byte{}, c.GenesisValidatorRoot(), "Did not get correct genesis validator root")
+	assert.Equal(t, [32]byte{}, c.GenesisValidatorsRoot(), "Did not get correct genesis validators root")

 	s, err := v1.InitializeFromProto(&ethpb.BeaconState{GenesisValidatorsRoot: []byte{'a'}})
 	require.NoError(t, err)
 	c.head = &head{state: s}
-	assert.Equal(t, [32]byte{'a'}, c.GenesisValidatorRoot(), "Did not get correct genesis validator root")
+	assert.Equal(t, [32]byte{'a'}, c.GenesisValidatorsRoot(), "Did not get correct genesis validators root")
 }

 func TestHeadETH1Data_Nil(t *testing.T) {
@@ -221,7 +233,9 @@ func TestIsCanonical_Ok(t *testing.T) {
 	blk.Block.Slot = 0
 	root, err := blk.Block.HashTreeRoot()
 	require.NoError(t, err)
-	require.NoError(t, beaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(blk)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(blk)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))
 	require.NoError(t, beaconDB.SaveGenesisBlockRoot(ctx, root))
 	can, err := c.IsCanonical(ctx, root)
 	require.NoError(t, err)
@@ -264,51 +278,64 @@ func TestService_HeadSeed(t *testing.T) {
 	require.DeepEqual(t, seed, root)
 }

-func TestService_HeadGenesisValidatorRoot(t *testing.T) {
+func TestService_HeadGenesisValidatorsRoot(t *testing.T) {
 	s, _ := util.DeterministicGenesisState(t, 1)
 	c := &Service{}

 	c.head = &head{}
-	root := c.HeadGenesisValidatorRoot()
+	root := c.HeadGenesisValidatorsRoot()
 	require.Equal(t, [32]byte{}, root)

 	c.head = &head{state: s}
-	root = c.HeadGenesisValidatorRoot()
-	require.DeepEqual(t, root[:], s.GenesisValidatorRoot())
+	root = c.HeadGenesisValidatorsRoot()
+	require.DeepEqual(t, root[:], s.GenesisValidatorsRoot())
 }
-
-func TestService_ProtoArrayStore(t *testing.T) {
-	c := &Service{cfg: &Config{ForkChoiceStore: protoarray.New(0, 0, [32]byte{})}}
-	p := c.ProtoArrayStore()
-	require.Equal(t, 0, int(p.FinalizedEpoch()))
-}
-
-func TestService_ChainHeads(t *testing.T) {
+func TestService_ChainHeads_ProtoArray(t *testing.T) {
 	ctx := context.Background()
-	c := &Service{cfg: &Config{ForkChoiceStore: protoarray.New(0, 0, [32]byte{})}}
-	require.NoError(t, c.cfg.ForkChoiceStore.ProcessBlock(ctx, 100, [32]byte{'a'}, [32]byte{}, [32]byte{}, 0, 0))
-	require.NoError(t, c.cfg.ForkChoiceStore.ProcessBlock(ctx, 101, [32]byte{'b'}, [32]byte{'a'}, [32]byte{}, 0, 0))
-	require.NoError(t, c.cfg.ForkChoiceStore.ProcessBlock(ctx, 102, [32]byte{'c'}, [32]byte{'b'}, [32]byte{}, 0, 0))
-	require.NoError(t, c.cfg.ForkChoiceStore.ProcessBlock(ctx, 103, [32]byte{'d'}, [32]byte{}, [32]byte{}, 0, 0))
-	require.NoError(t, c.cfg.ForkChoiceStore.ProcessBlock(ctx, 104, [32]byte{'e'}, [32]byte{'b'}, [32]byte{}, 0, 0))
+	c := &Service{cfg: &config{ForkChoiceStore: protoarray.New(0, 0,
+		params.BeaconConfig().ZeroHash)}}
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 100, [32]byte{'a'}, [32]byte{}, params.BeaconConfig().ZeroHash, 0, 0))
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 101, [32]byte{'b'}, [32]byte{'a'}, params.BeaconConfig().ZeroHash, 0, 0))
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 102, [32]byte{'c'}, [32]byte{'b'}, params.BeaconConfig().ZeroHash, 0, 0))
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 103, [32]byte{'d'}, [32]byte{}, params.BeaconConfig().ZeroHash, 0, 0))
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 104, [32]byte{'e'}, [32]byte{'b'}, params.BeaconConfig().ZeroHash, 0, 0))

 	roots, slots := c.ChainHeads()
 	require.DeepEqual(t, [][32]byte{{'c'}, {'d'}, {'e'}}, roots)
 	require.DeepEqual(t, []types.Slot{102, 103, 104}, slots)
 }

+func TestService_ChainHeads_DoublyLinkedTree(t *testing.T) {
+	ctx := context.Background()
+	c := &Service{cfg: &config{ForkChoiceStore: doublylinkedtree.New(0, 0)}}
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 100, [32]byte{'a'}, [32]byte{}, params.BeaconConfig().ZeroHash, 0, 0))
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 101, [32]byte{'b'}, [32]byte{'a'}, params.BeaconConfig().ZeroHash, 0, 0))
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 102, [32]byte{'c'}, [32]byte{'b'}, params.BeaconConfig().ZeroHash, 0, 0))
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 103, [32]byte{'d'}, [32]byte{}, params.BeaconConfig().ZeroHash, 0, 0))
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 104, [32]byte{'e'}, [32]byte{'b'}, params.BeaconConfig().ZeroHash, 0, 0))
+
+	roots, slots := c.ChainHeads()
+	require.Equal(t, 3, len(roots))
+	rootMap := map[[32]byte]types.Slot{[32]byte{'c'}: 102, [32]byte{'d'}: 103, [32]byte{'e'}: 104}
+	for i, root := range roots {
+		slot, ok := rootMap[root]
+		require.Equal(t, true, ok)
+		require.Equal(t, slot, slots[i])
+	}
+}
+
 func TestService_HeadPublicKeyToValidatorIndex(t *testing.T) {
 	s, _ := util.DeterministicGenesisState(t, 10)
 	c := &Service{}
 	c.head = &head{state: s}

-	_, e := c.HeadPublicKeyToValidatorIndex(context.Background(), [48]byte{})
+	_, e := c.HeadPublicKeyToValidatorIndex([fieldparams.BLSPubkeyLength]byte{})
 	require.Equal(t, false, e)

 	v, err := s.ValidatorAtIndex(0)
 	require.NoError(t, err)

-	i, e := c.HeadPublicKeyToValidatorIndex(context.Background(), bytesutil.ToBytes48(v.PublicKey))
+	i, e := c.HeadPublicKeyToValidatorIndex(bytesutil.ToBytes48(v.PublicKey))
 	require.Equal(t, true, e)
 	require.Equal(t, types.ValidatorIndex(0), i)
 }
@@ -317,12 +344,12 @@ func TestService_HeadPublicKeyToValidatorIndexNil(t *testing.T) {
 	c := &Service{}
 	c.head = nil

-	idx, e := c.HeadPublicKeyToValidatorIndex(context.Background(), [48]byte{})
+	idx, e := c.HeadPublicKeyToValidatorIndex([fieldparams.BLSPubkeyLength]byte{})
 	require.Equal(t, false, e)
 	require.Equal(t, types.ValidatorIndex(0), idx)

 	c.head = &head{state: nil}
-	i, e := c.HeadPublicKeyToValidatorIndex(context.Background(), [48]byte{})
+	i, e := c.HeadPublicKeyToValidatorIndex([fieldparams.BLSPubkeyLength]byte{})
 	require.Equal(t, false, e)
 	require.Equal(t, types.ValidatorIndex(0), i)
 }
@@ -347,10 +374,160 @@ func TestService_HeadValidatorIndexToPublicKeyNil(t *testing.T) {

 	p, err := c.HeadValidatorIndexToPublicKey(context.Background(), 0)
 	require.NoError(t, err)
-	require.Equal(t, [48]byte{}, p)
+	require.Equal(t, [fieldparams.BLSPubkeyLength]byte{}, p)

 	c.head = &head{state: nil}
 	p, err = c.HeadValidatorIndexToPublicKey(context.Background(), 0)
 	require.NoError(t, err)
-	require.Equal(t, [48]byte{}, p)
+	require.Equal(t, [fieldparams.BLSPubkeyLength]byte{}, p)
+}
+
+func TestService_IsOptimistic_ProtoArray(t *testing.T) {
+	params.SetupTestConfigCleanup(t)
+	cfg := params.BeaconConfig()
+	cfg.BellatrixForkEpoch = 0
+	params.OverrideBeaconConfig(cfg)
+
+	ctx := context.Background()
+	c := &Service{cfg: &config{ForkChoiceStore: protoarray.New(0, 0, [32]byte{})}, head: &head{slot: 101, root: [32]byte{'b'}}}
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 100, [32]byte{'a'}, [32]byte{}, params.BeaconConfig().ZeroHash, 0, 0))
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 101, [32]byte{'b'}, [32]byte{'a'}, params.BeaconConfig().ZeroHash, 0, 0))
+
+	opt, err := c.IsOptimistic(ctx)
+	require.NoError(t, err)
+	require.Equal(t, true, opt)
+}
+
+func TestService_IsOptimistic_DoublyLinkedTree(t *testing.T) {
+	params.SetupTestConfigCleanup(t)
+	cfg := params.BeaconConfig()
+	cfg.BellatrixForkEpoch = 0
+	params.OverrideBeaconConfig(cfg)
+
+	ctx := context.Background()
+	c := &Service{cfg: &config{ForkChoiceStore: doublylinkedtree.New(0, 0)}, head: &head{slot: 101, root: [32]byte{'b'}}}
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 100, [32]byte{'a'}, [32]byte{}, params.BeaconConfig().ZeroHash, 0, 0))
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 101, [32]byte{'b'}, [32]byte{'a'}, params.BeaconConfig().ZeroHash, 0, 0))
+
+	opt, err := c.IsOptimistic(ctx)
+	require.NoError(t, err)
+	require.Equal(t, true, opt)
+}
+
+func TestService_IsOptimisticBeforeBellatrix(t *testing.T) {
+	ctx := context.Background()
+	c := &Service{genesisTime: time.Now()}
+	opt, err := c.IsOptimistic(ctx)
+	require.NoError(t, err)
+	require.Equal(t, false, opt)
+}
+
+func TestService_IsOptimisticForRoot_ProtoArray(t *testing.T) {
+	ctx := context.Background()
+	c := &Service{cfg: &config{ForkChoiceStore: protoarray.New(0, 0, [32]byte{})}, head: &head{slot: 101, root: [32]byte{'b'}}}
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 100, [32]byte{'a'}, [32]byte{}, params.BeaconConfig().ZeroHash, 0, 0))
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 101, [32]byte{'b'}, [32]byte{'a'}, params.BeaconConfig().ZeroHash, 0, 0))
+
+	opt, err := c.IsOptimisticForRoot(ctx, [32]byte{'a'})
+	require.NoError(t, err)
+	require.Equal(t, true, opt)
+}
+
+func TestService_IsOptimisticForRoot_DoublyLinkedTree(t *testing.T) {
+	ctx := context.Background()
+	c := &Service{cfg: &config{ForkChoiceStore: doublylinkedtree.New(0, 0)}, head: &head{slot: 101, root: [32]byte{'b'}}}
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 100, [32]byte{'a'}, [32]byte{}, params.BeaconConfig().ZeroHash, 0, 0))
+	require.NoError(t, c.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 101, [32]byte{'b'}, [32]byte{'a'}, params.BeaconConfig().ZeroHash, 0, 0))
+
+	opt, err := c.IsOptimisticForRoot(ctx, [32]byte{'a'})
+	require.NoError(t, err)
+	require.Equal(t, true, opt)
+}
+
+func TestService_IsOptimisticForRoot_DB_ProtoArray(t *testing.T) {
+	beaconDB := testDB.SetupDB(t)
+	ctx := context.Background()
+	c := &Service{cfg: &config{BeaconDB: beaconDB, ForkChoiceStore: protoarray.New(0, 0, [32]byte{})}, head: &head{slot: 101, root: [32]byte{'b'}}}
+	c.head = &head{root: params.BeaconConfig().ZeroHash}
+	b := util.NewBeaconBlock()
+	b.Block.Slot = 10
+	br, err := b.Block.HashTreeRoot()
+	require.NoError(t, err)
+	wsb, err := wrapper.WrappedSignedBeaconBlock(b)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(context.Background(), wsb))
+	require.NoError(t, beaconDB.SaveStateSummary(context.Background(), &ethpb.StateSummary{Root: br[:], Slot: 10}))
+
+	optimisticBlock := util.NewBeaconBlock()
+	optimisticBlock.Block.Slot = 11
+	optimisticRoot, err := optimisticBlock.Block.HashTreeRoot()
+	require.NoError(t, err)
+	wsb, err = wrapper.WrappedSignedBeaconBlock(optimisticBlock)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(context.Background(), wsb))
+
+	validatedBlock := util.NewBeaconBlock()
+	validatedBlock.Block.Slot = 9
+	validatedRoot, err := validatedBlock.Block.HashTreeRoot()
+	require.NoError(t, err)
+	wsb, err = wrapper.WrappedSignedBeaconBlock(validatedBlock)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(context.Background(), wsb))
+
+	validatedCheckpoint := &ethpb.Checkpoint{Root: br[:]}
+	require.NoError(t, beaconDB.SaveLastValidatedCheckpoint(ctx, validatedCheckpoint))
+
+	require.NoError(t, beaconDB.SaveStateSummary(context.Background(), &ethpb.StateSummary{Root: optimisticRoot[:], Slot: 11}))
+	optimistic, err := c.IsOptimisticForRoot(ctx, optimisticRoot)
+	require.NoError(t, err)
+	require.Equal(t, true, optimistic)
+
+	require.NoError(t, beaconDB.SaveStateSummary(context.Background(), &ethpb.StateSummary{Root: validatedRoot[:], Slot: 9}))
+	validated, err := c.IsOptimisticForRoot(ctx, validatedRoot)
+	require.NoError(t, err)
+	require.Equal(t, false, validated)
+}
+
+func TestService_IsOptimisticForRoot__DB_DoublyLinkedTree(t *testing.T) {
+	beaconDB := testDB.SetupDB(t)
+	ctx := context.Background()
+	c := &Service{cfg: &config{BeaconDB: beaconDB, ForkChoiceStore: doublylinkedtree.New(0, 0)}, head: &head{slot: 101, root: [32]byte{'b'}}}
+	c.head = &head{root: params.BeaconConfig().ZeroHash}
+	b := util.NewBeaconBlock()
+	b.Block.Slot = 10
+	br, err := b.Block.HashTreeRoot()
+	require.NoError(t, err)
+	wsb, err := wrapper.WrappedSignedBeaconBlock(b)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(context.Background(), wsb))
+	require.NoError(t, beaconDB.SaveStateSummary(context.Background(), &ethpb.StateSummary{Root: br[:], Slot: 10}))
+
+	optimisticBlock := util.NewBeaconBlock()
+	optimisticBlock.Block.Slot = 11
+	optimisticRoot, err := optimisticBlock.Block.HashTreeRoot()
+	require.NoError(t, err)
+	wsb, err = wrapper.WrappedSignedBeaconBlock(optimisticBlock)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(context.Background(), wsb))
+
+	validatedBlock := util.NewBeaconBlock()
+	validatedBlock.Block.Slot = 9
+	validatedRoot, err := validatedBlock.Block.HashTreeRoot()
+	require.NoError(t, err)
+	wsb, err = wrapper.WrappedSignedBeaconBlock(validatedBlock)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(context.Background(), wsb))
+
+	validatedCheckpoint := &ethpb.Checkpoint{Root: br[:]}
+	require.NoError(t, beaconDB.SaveLastValidatedCheckpoint(ctx, validatedCheckpoint))
+
+	require.NoError(t, beaconDB.SaveStateSummary(context.Background(), &ethpb.StateSummary{Root: optimisticRoot[:], Slot: 11}))
+	optimistic, err := c.IsOptimisticForRoot(ctx, optimisticRoot)
+	require.NoError(t, err)
+	require.Equal(t, true, optimistic)
+
+	require.NoError(t, beaconDB.SaveStateSummary(context.Background(), &ethpb.StateSummary{Root: validatedRoot[:], Slot: 9}))
+	validated, err := c.IsOptimisticForRoot(ctx, validatedRoot)
+	require.NoError(t, err)
+	require.Equal(t, false, validated)
 }
--- a/beacon-chain/blockchain/checktags_test.go
+++ b/beacon-chain/blockchain/checktags_test.go
@@ -1,3 +1,4 @@
+//go:build !develop
 // +build !develop

 package blockchain
--- a/beacon-chain/blockchain/error.go
+++ b/beacon-chain/blockchain/error.go
@@ -0,0 +1,19 @@
+package blockchain
+
+import "github.com/pkg/errors"
+
+var (
+	// errNilJustifiedInStore is returned when a nil justified checkpt is returned from store.
+	errNilJustifiedInStore = errors.New("nil justified checkpoint returned from store")
+	// errNilBestJustifiedInStore is returned when a nil justified checkpt is returned from store.
+	errNilBestJustifiedInStore = errors.New("nil best justified checkpoint returned from store")
+	// errNilFinalizedInStore is returned when a nil finalized checkpt is returned from store.
+	errNilFinalizedInStore = errors.New("nil finalized checkpoint returned from store")
+	// errInvalidNilSummary is returned when a nil summary is returned from the DB.
+	errInvalidNilSummary = errors.New("nil summary returned from the DB")
+	// errNilParentInDB is returned when a nil parent block is returned from the DB.
+	errNilParentInDB = errors.New("nil parent block in DB")
+	// errWrongBlockCound is returned when the wrong number of blocks or
+	// block roots is used
+	errWrongBlockCount = errors.New("wrong number of blocks or block roots")
+)
--- a/beacon-chain/blockchain/head.go
+++ b/beacon-chain/blockchain/head.go
@@ -10,10 +10,11 @@ import (
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/feed"
 	statefeed "github.com/prysmaticlabs/prysm/beacon-chain/core/feed/state"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
-	"github.com/prysmaticlabs/prysm/beacon-chain/core/time"
+	doublylinkedtree "github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/doubly-linked-tree"
 	"github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/protoarray"
 	"github.com/prysmaticlabs/prysm/beacon-chain/state"
 	"github.com/prysmaticlabs/prysm/config/features"
+	fieldparams "github.com/prysmaticlabs/prysm/config/fieldparams"
 	"github.com/prysmaticlabs/prysm/config/params"
 	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
 	ethpbv1 "github.com/prysmaticlabs/prysm/proto/eth/v1"
@@ -23,6 +24,21 @@ import (
 	"go.opencensus.io/trace"
 )

+// UpdateHeadWithBalances updates the beacon state head after getting justified balanced from cache.
+func (s *Service) UpdateHeadWithBalances(ctx context.Context) error {
+	cp := s.store.JustifiedCheckpt()
+	if cp == nil {
+		return errors.New("no justified checkpoint")
+	}
+	balances, err := s.justifiedBalances.get(ctx, bytesutil.ToBytes32(cp.Root))
+	if err != nil {
+		msg := fmt.Sprintf("could not read balances for state w/ justified checkpoint %#x", cp.Root)
+		return errors.Wrap(err, msg)
+	}
+
+	return s.updateHead(ctx, balances)
+}
+
 // This defines the current chain service's view of head.
 type head struct {
 	slot  types.Slot              // current head slot.
@@ -37,24 +53,20 @@ func (s *Service) updateHead(ctx context.Context, balances []uint64) error {
 	ctx, span := trace.StartSpan(ctx, "blockChain.updateHead")
 	defer span.End()

-	// To get the proper head update, a node first checks its best justified
-	// can become justified. This is designed to prevent bounce attack and
-	// ensure head gets its best justified info.
-	if s.bestJustifiedCheckpt.Epoch > s.justifiedCheckpt.Epoch {
-		s.justifiedCheckpt = s.bestJustifiedCheckpt
-		if err := s.cacheJustifiedStateBalances(ctx, bytesutil.ToBytes32(s.justifiedCheckpt.Root)); err != nil {
-			return err
-		}
-	}
-
 	// Get head from the fork choice service.
-	f := s.finalizedCheckpt
-	j := s.justifiedCheckpt
-	// To get head before the first justified epoch, the fork choice will start with genesis root
+	f := s.store.FinalizedCheckpt()
+	if f == nil {
+		return errNilFinalizedInStore
+	}
+	j := s.store.JustifiedCheckpt()
+	if j == nil {
+		return errNilJustifiedInStore
+	}
+	// To get head before the first justified epoch, the fork choice will start with origin root
 	// instead of zero hashes.
 	headStartRoot := bytesutil.ToBytes32(j.Root)
 	if headStartRoot == params.BeaconConfig().ZeroHash {
-		headStartRoot = s.genesisRoot
+		headStartRoot = s.originBlockRoot
 	}

 	// In order to process head, fork choice store requires justified info.
@@ -66,7 +78,11 @@ func (s *Service) updateHead(ctx context.Context, balances []uint64) error {
 		if err != nil {
 			return err
 		}
-		s.cfg.ForkChoiceStore = protoarray.New(j.Epoch, f.Epoch, bytesutil.ToBytes32(f.Root))
+		if features.Get().EnableForkChoiceDoublyLinkedTree {
+			s.cfg.ForkChoiceStore = doublylinkedtree.New(j.Epoch, f.Epoch)
+		} else {
+			s.cfg.ForkChoiceStore = protoarray.New(j.Epoch, f.Epoch, bytesutil.ToBytes32(f.Root))
+		}
 		if err := s.insertBlockToForkChoiceStore(ctx, jb.Block(), headStartRoot, f, j); err != nil {
 			return err
 		}
@@ -107,8 +123,8 @@ func (s *Service) saveHead(ctx context.Context, headRoot [32]byte) error {
 	if err != nil {
 		return err
 	}
-	if newHeadBlock == nil || newHeadBlock.IsNil() || newHeadBlock.Block().IsNil() {
-		return errors.New("cannot save nil head block")
+	if err := helpers.BeaconBlockIsNil(newHeadBlock); err != nil {
+		return err
 	}

 	// Get the new head state from cached state or DB.
@@ -132,16 +148,21 @@ func (s *Service) saveHead(ctx context.Context, headRoot [32]byte) error {
 			"oldSlot": fmt.Sprintf("%d", headSlot),
 		}).Debug("Chain reorg occurred")
 		absoluteSlotDifference := slots.AbsoluteValueSlotDifference(newHeadSlot, headSlot)
+		isOptimistic, err := s.IsOptimistic(ctx)
+		if err != nil {
+			return errors.Wrap(err, "could not check if node is optimistically synced")
+		}
 		s.cfg.StateNotifier.StateFeed().Send(&feed.Event{
 			Type: statefeed.Reorg,
 			Data: &ethpbv1.EventChainReorg{
-				Slot:         newHeadSlot,
-				Depth:        absoluteSlotDifference,
-				OldHeadBlock: oldHeadRoot[:],
-				NewHeadBlock: headRoot[:],
-				OldHeadState: oldStateRoot,
-				NewHeadState: newStateRoot,
-				Epoch:        slots.ToEpoch(newHeadSlot),
+				Slot:                newHeadSlot,
+				Depth:               absoluteSlotDifference,
+				OldHeadBlock:        oldHeadRoot[:],
+				NewHeadBlock:        headRoot[:],
+				OldHeadState:        oldStateRoot,
+				NewHeadState:        newStateRoot,
+				Epoch:               slots.ToEpoch(newHeadSlot),
+				ExecutionOptimistic: isOptimistic,
 			},
 		})

@@ -163,7 +184,7 @@ func (s *Service) saveHead(ctx context.Context, headRoot [32]byte) error {
 	// Forward an event capturing a new chain head over a common event feed
 	// done in a goroutine to avoid blocking the critical runtime main routine.
 	go func() {
-		if err := s.notifyNewHeadEvent(newHeadSlot, newHeadState, newStateRoot, headRoot[:]); err != nil {
+		if err := s.notifyNewHeadEvent(ctx, newHeadSlot, newHeadState, newStateRoot, headRoot[:]); err != nil {
 			log.WithError(err).Error("Could not notify event feed of new chain head")
 		}
 	}()
@@ -175,7 +196,7 @@ func (s *Service) saveHead(ctx context.Context, headRoot [32]byte) error {
 // root in DB. With the inception of initial-sync-cache-state flag, it uses finalized
 // check point as anchors to resume sync therefore head is no longer needed to be saved on per slot basis.
 func (s *Service) saveHeadNoDB(ctx context.Context, b block.SignedBeaconBlock, r [32]byte, hs state.BeaconState) error {
-	if err := helpers.VerifyNilBeaconBlock(b); err != nil {
+	if err := helpers.BeaconBlockIsNil(b); err != nil {
 		return err
 	}
 	cachedHeadRoot, err := s.HeadRoot(ctx)
@@ -248,16 +269,16 @@ func (s *Service) headBlock() block.SignedBeaconBlock {
 // It does a full copy on head state for immutability.
 // This is a lock free version.
 func (s *Service) headState(ctx context.Context) state.BeaconState {
-	ctx, span := trace.StartSpan(ctx, "blockChain.headState")
+	_, span := trace.StartSpan(ctx, "blockChain.headState")
 	defer span.End()

 	return s.head.state.Copy()
 }

-// This returns the genesis validator root of the head state.
+// This returns the genesis validators root of the head state.
 // This is a lock free version.
-func (s *Service) headGenesisValidatorRoot() [32]byte {
-	return bytesutil.ToBytes32(s.head.state.GenesisValidatorRoot())
+func (s *Service) headGenesisValidatorsRoot() [32]byte {
+	return bytesutil.ToBytes32(s.head.state.GenesisValidatorsRoot())
 }

 // This returns the validator referenced by the provided index in
@@ -267,73 +288,30 @@ func (s *Service) headValidatorAtIndex(index types.ValidatorIndex) (state.ReadOn
 	return s.head.state.ValidatorAtIndexReadOnly(index)
 }

+// This returns the validator index referenced by the provided pubkey in
+// the head state.
+// This is a lock free version.
+func (s *Service) headValidatorIndexAtPubkey(pubKey [fieldparams.BLSPubkeyLength]byte) (types.ValidatorIndex, bool) {
+	return s.head.state.ValidatorIndexByPubkey(pubKey)
+}
+
 // Returns true if head state exists.
 // This is the lock free version.
 func (s *Service) hasHeadState() bool {
 	return s.head != nil && s.head.state != nil
 }

-// This caches justified state balances to be used for fork choice.
-func (s *Service) cacheJustifiedStateBalances(ctx context.Context, justifiedRoot [32]byte) error {
-	if err := s.cfg.BeaconDB.SaveBlocks(ctx, s.getInitSyncBlocks()); err != nil {
-		return err
-	}
-
-	s.clearInitSyncBlocks()
-
-	var justifiedState state.BeaconState
-	var err error
-	if justifiedRoot == s.genesisRoot {
-		justifiedState, err = s.cfg.BeaconDB.GenesisState(ctx)
-		if err != nil {
-			return err
-		}
-	} else {
-		justifiedState, err = s.cfg.StateGen.StateByRoot(ctx, justifiedRoot)
-		if err != nil {
-			return err
-		}
-	}
-	if justifiedState == nil || justifiedState.IsNil() {
-		return errors.New("justified state can't be nil")
-	}
-
-	epoch := time.CurrentEpoch(justifiedState)
-
-	justifiedBalances := make([]uint64, justifiedState.NumValidators())
-	if err := justifiedState.ReadFromEveryValidator(func(idx int, val state.ReadOnlyValidator) error {
-		if helpers.IsActiveValidatorUsingTrie(val, epoch) {
-			justifiedBalances[idx] = val.EffectiveBalance()
-		} else {
-			justifiedBalances[idx] = 0
-		}
-		return nil
-	}); err != nil {
-		return err
-	}
-
-	s.justifiedBalancesLock.Lock()
-	defer s.justifiedBalancesLock.Unlock()
-	s.justifiedBalances = justifiedBalances
-	return nil
-}
-
-func (s *Service) getJustifiedBalances() []uint64 {
-	s.justifiedBalancesLock.RLock()
-	defer s.justifiedBalancesLock.RUnlock()
-	return s.justifiedBalances
-}
-
 // Notifies a common event feed of a new chain head event. Called right after a new
 // chain head is determined, set, and saved to disk.
 func (s *Service) notifyNewHeadEvent(
+	ctx context.Context,
 	newHeadSlot types.Slot,
 	newHeadState state.BeaconState,
 	newHeadStateRoot,
 	newHeadRoot []byte,
 ) error {
-	previousDutyDependentRoot := s.genesisRoot[:]
-	currentDutyDependentRoot := s.genesisRoot[:]
+	previousDutyDependentRoot := s.originBlockRoot[:]
+	currentDutyDependentRoot := s.originBlockRoot[:]

 	var previousDutyEpoch types.Epoch
 	currentDutyEpoch := slots.ToEpoch(newHeadSlot)
@@ -360,6 +338,10 @@ func (s *Service) notifyNewHeadEvent(
 			return errors.Wrap(err, "could not get duty dependent root")
 		}
 	}
+	isOptimistic, err := s.IsOptimistic(ctx)
+	if err != nil {
+		return errors.Wrap(err, "could not check if node is optimistically synced")
+	}
 	s.cfg.StateNotifier.StateFeed().Send(&feed.Event{
 		Type: statefeed.NewHead,
 		Data: &ethpbv1.EventHead{
@@ -369,6 +351,7 @@ func (s *Service) notifyNewHeadEvent(
 			EpochTransition:           slots.IsEpochStart(newHeadSlot),
 			PreviousDutyDependentRoot: previousDutyDependentRoot,
 			CurrentDutyDependentRoot:  currentDutyDependentRoot,
+			ExecutionOptimistic:       isOptimistic,
 		},
 	})
 	return nil
--- a/beacon-chain/blockchain/head_sync_committee_info.go
+++ b/beacon-chain/blockchain/head_sync_committee_info.go
@@ -130,7 +130,7 @@ func (s *Service) domainWithHeadState(ctx context.Context, slot types.Slot, doma
 	if err != nil {
 		return nil, err
 	}
-	return signing.Domain(headState.Fork(), slots.ToEpoch(headState.Slot()), domain, headState.GenesisValidatorRoot())
+	return signing.Domain(headState.Fork(), slots.ToEpoch(headState.Slot()), domain, headState.GenesisValidatorsRoot())
 }

 // returns the head state that is advanced up to `slot`. It utilizes the cache `syncCommitteeHeadState` by retrieving using `slot` as key.
@@ -157,11 +157,9 @@ func (s *Service) getSyncCommitteeHeadState(ctx context.Context, slot types.Slot
 		if headState == nil || headState.IsNil() {
 			return nil, errors.New("nil state")
 		}
-		if slot > headState.Slot() {
-			headState, err = transition.ProcessSlots(ctx, headState, slot)
-			if err != nil {
-				return nil, err
-			}
+		headState, err = transition.ProcessSlotsIfPossible(ctx, headState, slot)
+		if err != nil {
+			return nil, err
 		}
 		syncHeadStateMiss.Inc()
 		err = syncCommitteeHeadStateCache.Put(slot, headState)
--- a/beacon-chain/blockchain/head_sync_committee_info_test.go
+++ b/beacon-chain/blockchain/head_sync_committee_info_test.go
@@ -18,7 +18,7 @@ import (
 func TestService_headSyncCommitteeFetcher_Errors(t *testing.T) {
 	beaconDB := dbtest.SetupDB(t)
 	c := &Service{
-		cfg: &Config{
+		cfg: &config{
 			StateGen: stategen.New(beaconDB),
 		},
 	}
@@ -36,7 +36,7 @@ func TestService_headSyncCommitteeFetcher_Errors(t *testing.T) {
 func TestService_HeadDomainFetcher_Errors(t *testing.T) {
 	beaconDB := dbtest.SetupDB(t)
 	c := &Service{
-		cfg: &Config{
+		cfg: &config{
 			StateGen: stategen.New(beaconDB),
 		},
 	}
@@ -122,7 +122,7 @@ func TestService_HeadSyncCommitteeDomain(t *testing.T) {
 	c := &Service{}
 	c.head = &head{state: s}

-	wanted, err := signing.Domain(s.Fork(), slots.ToEpoch(s.Slot()), params.BeaconConfig().DomainSyncCommittee, s.GenesisValidatorRoot())
+	wanted, err := signing.Domain(s.Fork(), slots.ToEpoch(s.Slot()), params.BeaconConfig().DomainSyncCommittee, s.GenesisValidatorsRoot())
 	require.NoError(t, err)

 	d, err := c.HeadSyncCommitteeDomain(context.Background(), 0)
@@ -136,7 +136,7 @@ func TestService_HeadSyncContributionProofDomain(t *testing.T) {
 	c := &Service{}
 	c.head = &head{state: s}

-	wanted, err := signing.Domain(s.Fork(), slots.ToEpoch(s.Slot()), params.BeaconConfig().DomainContributionAndProof, s.GenesisValidatorRoot())
+	wanted, err := signing.Domain(s.Fork(), slots.ToEpoch(s.Slot()), params.BeaconConfig().DomainContributionAndProof, s.GenesisValidatorsRoot())
 	require.NoError(t, err)

 	d, err := c.HeadSyncContributionProofDomain(context.Background(), 0)
@@ -150,7 +150,7 @@ func TestService_HeadSyncSelectionProofDomain(t *testing.T) {
 	c := &Service{}
 	c.head = &head{state: s}

-	wanted, err := signing.Domain(s.Fork(), slots.ToEpoch(s.Slot()), params.BeaconConfig().DomainSyncCommitteeSelectionProof, s.GenesisValidatorRoot())
+	wanted, err := signing.Domain(s.Fork(), slots.ToEpoch(s.Slot()), params.BeaconConfig().DomainSyncCommitteeSelectionProof, s.GenesisValidatorsRoot())
 	require.NoError(t, err)

 	d, err := c.HeadSyncSelectionProofDomain(context.Background(), 0)
--- a/beacon-chain/blockchain/head_test.go
+++ b/beacon-chain/blockchain/head_test.go
@@ -39,9 +39,10 @@ func TestSaveHead_Different(t *testing.T) {
 	service := setupBeaconChain(t, beaconDB)

 	util.NewBeaconBlock()
-	oldBlock := wrapper.WrappedPhase0SignedBeaconBlock(
+	oldBlock, err := wrapper.WrappedSignedBeaconBlock(
 		util.NewBeaconBlock(),
 	)
+	require.NoError(t, err)
 	require.NoError(t, service.cfg.BeaconDB.SaveBlock(context.Background(), oldBlock))
 	oldRoot, err := oldBlock.Block().HashTreeRoot()
 	require.NoError(t, err)
@@ -55,7 +56,9 @@ func TestSaveHead_Different(t *testing.T) {
 	newHeadSignedBlock.Block.Slot = 1
 	newHeadBlock := newHeadSignedBlock.Block

-	require.NoError(t, service.cfg.BeaconDB.SaveBlock(context.Background(), wrapper.WrappedPhase0SignedBeaconBlock(newHeadSignedBlock)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(newHeadSignedBlock)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(context.Background(), wsb))
 	newRoot, err := newHeadBlock.HashTreeRoot()
 	require.NoError(t, err)
 	headState, err := util.NewBeaconState()
@@ -80,9 +83,10 @@ func TestSaveHead_Different_Reorg(t *testing.T) {
 	beaconDB := testDB.SetupDB(t)
 	service := setupBeaconChain(t, beaconDB)

-	oldBlock := wrapper.WrappedPhase0SignedBeaconBlock(
+	oldBlock, err := wrapper.WrappedSignedBeaconBlock(
 		util.NewBeaconBlock(),
 	)
+	require.NoError(t, err)
 	require.NoError(t, service.cfg.BeaconDB.SaveBlock(context.Background(), oldBlock))
 	oldRoot, err := oldBlock.Block().HashTreeRoot()
 	require.NoError(t, err)
@@ -98,7 +102,9 @@ func TestSaveHead_Different_Reorg(t *testing.T) {
 	newHeadSignedBlock.Block.ParentRoot = reorgChainParent[:]
 	newHeadBlock := newHeadSignedBlock.Block

-	require.NoError(t, service.cfg.BeaconDB.SaveBlock(context.Background(), wrapper.WrappedPhase0SignedBeaconBlock(newHeadSignedBlock)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(newHeadSignedBlock)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(context.Background(), wsb))
 	newRoot, err := newHeadBlock.HashTreeRoot()
 	require.NoError(t, err)
 	headState, err := util.NewBeaconState()
@@ -123,13 +129,15 @@ func TestSaveHead_Different_Reorg(t *testing.T) {
 func TestCacheJustifiedStateBalances_CanCache(t *testing.T) {
 	beaconDB := testDB.SetupDB(t)
 	service := setupBeaconChain(t, beaconDB)
+	ctx := context.Background()

 	state, _ := util.DeterministicGenesisState(t, 100)
 	r := [32]byte{'a'}
 	require.NoError(t, service.cfg.BeaconDB.SaveStateSummary(context.Background(), &ethpb.StateSummary{Root: r[:]}))
 	require.NoError(t, service.cfg.BeaconDB.SaveState(context.Background(), state, r))
-	require.NoError(t, service.cacheJustifiedStateBalances(context.Background(), r))
-	require.DeepEqual(t, service.getJustifiedBalances(), state.Balances(), "Incorrect justified balances")
+	balances, err := service.justifiedBalances.get(ctx, r)
+	require.NoError(t, err)
+	require.DeepEqual(t, balances, state.Balances(), "Incorrect justified balances")
 }

 func TestUpdateHead_MissingJustifiedRoot(t *testing.T) {
@@ -137,13 +145,15 @@ func TestUpdateHead_MissingJustifiedRoot(t *testing.T) {
 	service := setupBeaconChain(t, beaconDB)

 	b := util.NewBeaconBlock()
-	require.NoError(t, service.cfg.BeaconDB.SaveBlock(context.Background(), wrapper.WrappedPhase0SignedBeaconBlock(b)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(b)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(context.Background(), wsb))
 	r, err := b.Block.HashTreeRoot()
 	require.NoError(t, err)

-	service.justifiedCheckpt = &ethpb.Checkpoint{Root: r[:]}
-	service.finalizedCheckpt = &ethpb.Checkpoint{}
-	service.bestJustifiedCheckpt = &ethpb.Checkpoint{}
+	service.store.SetJustifiedCheckpt(&ethpb.Checkpoint{Root: r[:]})
+	service.store.SetFinalizedCheckpt(&ethpb.Checkpoint{})
+	service.store.SetBestJustifiedCheckpt(&ethpb.Checkpoint{})

 	require.NoError(t, service.updateHead(context.Background(), []uint64{}))
 }
@@ -153,14 +163,14 @@ func Test_notifyNewHeadEvent(t *testing.T) {
 		bState, _ := util.DeterministicGenesisState(t, 10)
 		notifier := &mock.MockStateNotifier{RecordEvents: true}
 		srv := &Service{
-			cfg: &Config{
+			cfg: &config{
 				StateNotifier: notifier,
 			},
-			genesisRoot: [32]byte{1},
+			originBlockRoot: [32]byte{1},
 		}
 		newHeadStateRoot := [32]byte{2}
 		newHeadRoot := [32]byte{3}
-		err := srv.notifyNewHeadEvent(1, bState, newHeadStateRoot[:], newHeadRoot[:])
+		err := srv.notifyNewHeadEvent(context.Background(), 1, bState, newHeadStateRoot[:], newHeadRoot[:])
 		require.NoError(t, err)
 		events := notifier.ReceivedEvents()
 		require.Equal(t, 1, len(events))
@@ -172,8 +182,8 @@ func Test_notifyNewHeadEvent(t *testing.T) {
 			Block:                     newHeadRoot[:],
 			State:                     newHeadStateRoot[:],
 			EpochTransition:           false,
-			PreviousDutyDependentRoot: srv.genesisRoot[:],
-			CurrentDutyDependentRoot:  srv.genesisRoot[:],
+			PreviousDutyDependentRoot: srv.originBlockRoot[:],
+			CurrentDutyDependentRoot:  srv.originBlockRoot[:],
 		}
 		require.DeepSSZEqual(t, wanted, eventHead)
 	})
@@ -182,10 +192,10 @@ func Test_notifyNewHeadEvent(t *testing.T) {
 		notifier := &mock.MockStateNotifier{RecordEvents: true}
 		genesisRoot := [32]byte{1}
 		srv := &Service{
-			cfg: &Config{
+			cfg: &config{
 				StateNotifier: notifier,
 			},
-			genesisRoot: genesisRoot,
+			originBlockRoot: genesisRoot,
 		}
 		epoch1Start, err := slots.EpochStart(1)
 		require.NoError(t, err)
@@ -195,7 +205,7 @@ func Test_notifyNewHeadEvent(t *testing.T) {

 		newHeadStateRoot := [32]byte{2}
 		newHeadRoot := [32]byte{3}
-		err = srv.notifyNewHeadEvent(epoch2Start, bState, newHeadStateRoot[:], newHeadRoot[:])
+		err = srv.notifyNewHeadEvent(context.Background(), epoch2Start, bState, newHeadStateRoot[:], newHeadRoot[:])
 		require.NoError(t, err)
 		events := notifier.ReceivedEvents()
 		require.Equal(t, 1, len(events))
@@ -231,7 +241,9 @@ func TestSaveOrphanedAtts(t *testing.T) {
 	service := setupBeaconChain(t, beaconDB)
 	service.genesisTime = time.Now()

-	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(b)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(b)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wsb))
 	require.NoError(t, service.saveOrphanedAtts(ctx, r))

 	require.Equal(t, len(b.Block.Body.Attestations), service.cfg.AttPool.AggregatedAttestationCount())
@@ -257,7 +269,9 @@ func TestSaveOrphanedAtts_CanFilter(t *testing.T) {
 	service := setupBeaconChain(t, beaconDB)
 	service.genesisTime = time.Now().Add(time.Duration(-1*int64(params.BeaconConfig().SlotsPerEpoch+1)*int64(params.BeaconConfig().SecondsPerSlot)) * time.Second)

-	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(b)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(b)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wsb))
 	require.NoError(t, service.saveOrphanedAtts(ctx, r))

 	require.Equal(t, 0, service.cfg.AttPool.AggregatedAttestationCount())
--- a/beacon-chain/blockchain/info.go
+++ b/beacon-chain/blockchain/info.go
@@ -1,99 +0,0 @@
-package blockchain
-
-import (
-	"encoding/hex"
-	"fmt"
-	"net/http"
-
-	"github.com/emicklei/dot"
-	"github.com/prysmaticlabs/prysm/config/params"
-)
-
-const template = `<html>
-<head>
-    <script src="//cdnjs.cloudflare.com/ajax/libs/viz.js/2.1.2/viz.js"></script>
-    <script src="//cdnjs.cloudflare.com/ajax/libs/viz.js/2.1.2/full.render.js"></script>
-<body>
-    <script type="application/javascript">
-        var graph = ` + "`%s`;" + `
-        var viz = new Viz();
-        viz.renderSVGElement(graph) // reading the graph.
-            .then(function(element) {
-                document.body.appendChild(element); // appends to document.
-            })
-            .catch(error => {
-                // Create a new Viz instance (@see Caveats page for more info)
-                viz = new Viz();
-                // Possibly display the error
-                console.error(error);
-            });
-    </script>
-</head>
-</body>
-</html>`
-
-// TreeHandler is a handler to serve /tree page in metrics.
-func (s *Service) TreeHandler(w http.ResponseWriter, r *http.Request) {
-	headState, err := s.HeadState(r.Context())
-	if err != nil {
-		log.WithError(err).Error("Could not get head state")
-		return
-	}
-	if headState == nil || headState.IsNil() {
-		if _, err := w.Write([]byte("Unavailable during initial syncing")); err != nil {
-			log.WithError(err).Error("Failed to render p2p info page")
-		}
-	}
-
-	nodes := s.cfg.ForkChoiceStore.Nodes()
-
-	graph := dot.NewGraph(dot.Directed)
-	graph.Attr("rankdir", "RL")
-	graph.Attr("labeljust", "l")
-
-	dotNodes := make([]*dot.Node, len(nodes))
-	avgBalance := uint64(averageBalance(headState.Balances()))
-
-	for i := len(nodes) - 1; i >= 0; i-- {
-		// Construct label for each node.
-		slot := fmt.Sprintf("%d", nodes[i].Slot())
-		weight := fmt.Sprintf("%d", nodes[i].Weight()/1e9) // Convert unit Gwei to unit ETH.
-		votes := fmt.Sprintf("%d", nodes[i].Weight()/1e9/avgBalance)
-		index := fmt.Sprintf("%d", i)
-		g := nodes[i].Graffiti()
-		graffiti := hex.EncodeToString(g[:8])
-		label := "slot: " + slot + "\n votes: " + votes + "\n weight: " + weight + "\n graffiti: " + graffiti
-		var dotN dot.Node
-		if nodes[i].Parent() != ^uint64(0) {
-			dotN = graph.Node(index).Box().Attr("label", label)
-		}
-
-		if nodes[i].Slot() == s.HeadSlot() &&
-			nodes[i].BestDescendant() == ^uint64(0) &&
-			nodes[i].Parent() != ^uint64(0) {
-			dotN = dotN.Attr("color", "green")
-		}
-
-		dotNodes[i] = &dotN
-	}
-
-	for i := len(nodes) - 1; i >= 0; i-- {
-		if nodes[i].Parent() != ^uint64(0) && nodes[i].Parent() < uint64(len(dotNodes)) {
-			graph.Edge(*dotNodes[i], *dotNodes[nodes[i].Parent()])
-		}
-	}
-
-	w.WriteHeader(http.StatusOK)
-	w.Header().Set("Content-Type", "text/html")
-	if _, err := fmt.Fprintf(w, template, graph.String()); err != nil {
-		log.WithError(err).Error("Failed to render p2p info page")
-	}
-}
-
-func averageBalance(balances []uint64) float64 {
-	total := uint64(0)
-	for i := 0; i < len(balances); i++ {
-		total += balances[i]
-	}
-	return float64(total) / float64(len(balances)) / float64(params.BeaconConfig().GweiPerEth)
-}
--- a/beacon-chain/blockchain/info_test.go
+++ b/beacon-chain/blockchain/info_test.go
@@ -1,49 +0,0 @@
-package blockchain
-
-import (
-	"context"
-	"net/http"
-	"net/http/httptest"
-	"testing"
-
-	testDB "github.com/prysmaticlabs/prysm/beacon-chain/db/testing"
-	"github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/protoarray"
-	"github.com/prysmaticlabs/prysm/beacon-chain/state/stategen"
-	"github.com/prysmaticlabs/prysm/config/params"
-	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/wrapper"
-	"github.com/prysmaticlabs/prysm/testing/assert"
-	"github.com/prysmaticlabs/prysm/testing/require"
-	"github.com/prysmaticlabs/prysm/testing/util"
-)
-
-func TestService_TreeHandler(t *testing.T) {
-	req, err := http.NewRequest("GET", "/tree", nil)
-	require.NoError(t, err)
-
-	ctx := context.Background()
-	beaconDB := testDB.SetupDB(t)
-	headState, err := util.NewBeaconState()
-	require.NoError(t, err)
-	require.NoError(t, headState.SetBalances([]uint64{params.BeaconConfig().GweiPerEth}))
-	cfg := &Config{
-		BeaconDB: beaconDB,
-		ForkChoiceStore: protoarray.New(
-			0, // justifiedEpoch
-			0, // finalizedEpoch
-			[32]byte{'a'},
-		),
-		StateGen: stategen.New(beaconDB),
-	}
-	s, err := NewService(ctx, cfg)
-	require.NoError(t, err)
-	require.NoError(t, s.cfg.ForkChoiceStore.ProcessBlock(ctx, 0, [32]byte{'a'}, [32]byte{'g'}, [32]byte{'c'}, 0, 0))
-	require.NoError(t, s.cfg.ForkChoiceStore.ProcessBlock(ctx, 1, [32]byte{'b'}, [32]byte{'a'}, [32]byte{'c'}, 0, 0))
-	s.setHead([32]byte{'a'}, wrapper.WrappedPhase0SignedBeaconBlock(util.NewBeaconBlock()), headState)
-
-	rr := httptest.NewRecorder()
-	handler := http.HandlerFunc(s.TreeHandler)
-
-	handler.ServeHTTP(rr, req)
-
-	assert.Equal(t, http.StatusOK, rr.Code)
-}
--- a/beacon-chain/blockchain/log.go
+++ b/beacon-chain/blockchain/log.go
@@ -6,6 +6,7 @@ import (
 	"time"

 	"github.com/prysmaticlabs/prysm/config/params"
+	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
 	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
 	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/block"
 	"github.com/prysmaticlabs/prysm/runtime/version"
@@ -17,7 +18,7 @@ import (
 var log = logrus.WithField("prefix", "blockchain")

 // logs state transition related data every slot.
-func logStateTransitionData(b block.BeaconBlock) {
+func logStateTransitionData(b block.BeaconBlock) error {
 	log := log.WithField("slot", b.Slot())
 	if len(b.Body().Attestations()) > 0 {
 		log = log.WithField("attestations", len(b.Body().Attestations()))
@@ -34,13 +35,23 @@ func logStateTransitionData(b block.BeaconBlock) {
 	if len(b.Body().VoluntaryExits()) > 0 {
 		log = log.WithField("voluntaryExits", len(b.Body().VoluntaryExits()))
 	}
-	if b.Version() == version.Altair {
+	if b.Version() == version.Altair || b.Version() == version.Bellatrix {
 		agg, err := b.Body().SyncAggregate()
-		if err == nil {
-			log = log.WithField("syncBitsCount", agg.SyncCommitteeBits.Count())
+		if err != nil {
+			return err
 		}
+		log = log.WithField("syncBitsCount", agg.SyncCommitteeBits.Count())
+	}
+	if b.Version() == version.Bellatrix {
+		p, err := b.Body().ExecutionPayload()
+		if err != nil {
+			return err
+		}
+		log = log.WithField("payloadHash", fmt.Sprintf("%#x", bytesutil.Trunc(p.BlockHash)))
+		log = log.WithField("txCount", len(p.Transactions))
 	}
 	log.Info("Finished applying state transition")
+	return nil
 }

 func logBlockSyncStatus(block block.BeaconBlock, blockRoot [32]byte, finalized *ethpb.Checkpoint, receivedTime time.Time, genesisTime uint64) error {
@@ -55,6 +66,8 @@ func logBlockSyncStatus(block block.BeaconBlock, blockRoot [32]byte, finalized *
 		"epoch":          slots.ToEpoch(block.Slot()),
 		"finalizedEpoch": finalized.Epoch,
 		"finalizedRoot":  fmt.Sprintf("0x%s...", hex.EncodeToString(finalized.Root)[:8]),
+		"parentRoot":     fmt.Sprintf("0x%s...", hex.EncodeToString(block.ParentRoot())[:8]),
+		"version":        version.String(block.Version()),
 	}).Info("Synced new block")
 	log.WithFields(logrus.Fields{
 		"slot":                      block.Slot,
--- a/beacon-chain/blockchain/log_test.go
+++ b/beacon-chain/blockchain/log_test.go
@@ -3,6 +3,7 @@ package blockchain
 import (
 	"testing"

+	enginev1 "github.com/prysmaticlabs/prysm/proto/engine/v1"
 	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
 	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/block"
 	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/wrapper"
@@ -11,6 +12,17 @@ import (
 )

 func Test_logStateTransitionData(t *testing.T) {
+	payloadBlk := &ethpb.BeaconBlockBellatrix{
+		Body: &ethpb.BeaconBlockBodyBellatrix{
+			SyncAggregate: &ethpb.SyncAggregate{},
+			ExecutionPayload: &enginev1.ExecutionPayload{
+				BlockHash:    []byte{1, 2, 3},
+				Transactions: [][]byte{{}, {}},
+			},
+		},
+	}
+	wrappedPayloadBlk, err := wrapper.WrappedBeaconBlock(payloadBlk)
+	require.NoError(t, err)
 	tests := []struct {
 		name string
 		b    block.BeaconBlock
@@ -55,11 +67,15 @@ func Test_logStateTransitionData(t *testing.T) {
 				VoluntaryExits:    []*ethpb.SignedVoluntaryExit{{}}}}),
 			want: "\"Finished applying state transition\" attestations=1 attesterSlashings=1 deposits=1 prefix=blockchain proposerSlashings=1 slot=0 voluntaryExits=1",
 		},
+		{name: "has payload",
+			b:    wrappedPayloadBlk,
+			want: "\"Finished applying state transition\" payloadHash=0x010203 prefix=blockchain slot=0 syncBitsCount=0 txCount=2",
+		},
 	}
 	for _, tt := range tests {
 		hook := logTest.NewGlobal()
 		t.Run(tt.name, func(t *testing.T) {
-			logStateTransitionData(tt.b)
+			require.NoError(t, logStateTransitionData(tt.b))
 			require.LogsContain(t, hook, tt.want)
 		})
 	}
--- a/beacon-chain/blockchain/metrics.go
+++ b/beacon-chain/blockchain/metrics.go
@@ -130,6 +130,14 @@ var (
 		Name: "sync_head_state_hit",
 		Help: "The number of sync head state requests that are present in the cache.",
 	})
+	stateBalanceCacheHit = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "state_balance_cache_hit",
+		Help: "Count the number of state balance cache hits.",
+	})
+	stateBalanceCacheMiss = promauto.NewCounter(prometheus.CounterOpts{
+		Name: "state_balance_cache_miss",
+		Help: "Count the number of state balance cache hits.",
+	})
 )

 // reportSlotMetrics reports slot related metrics.
@@ -245,7 +253,7 @@ func reportEpochMetrics(ctx context.Context, postState, headState state.BeaconSt
 		if err != nil {
 			return err
 		}
-	case version.Altair:
+	case version.Altair, version.Bellatrix:
 		v, b, err = altair.InitializePrecomputeValidators(ctx, headState)
 		if err != nil {
 			return err
--- a/beacon-chain/blockchain/mock_engine_test.go
+++ b/beacon-chain/blockchain/mock_engine_test.go
@@ -0,0 +1,49 @@
+package blockchain
+
+import (
+	"context"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/pkg/errors"
+	enginev1 "github.com/prysmaticlabs/prysm/proto/engine/v1"
+)
+
+type mockEngineService struct {
+	newPayloadError error
+	forkchoiceError error
+	blks            map[[32]byte]*enginev1.ExecutionBlock
+}
+
+func (m *mockEngineService) NewPayload(context.Context, *enginev1.ExecutionPayload) ([]byte, error) {
+	return nil, m.newPayloadError
+}
+
+func (m *mockEngineService) ForkchoiceUpdated(context.Context, *enginev1.ForkchoiceState, *enginev1.PayloadAttributes) (*enginev1.PayloadIDBytes, []byte, error) {
+	return nil, nil, m.forkchoiceError
+}
+
+func (*mockEngineService) GetPayloadV1(
+	_ context.Context, _ enginev1.PayloadIDBytes,
+) *enginev1.ExecutionPayload {
+	return nil
+}
+
+func (*mockEngineService) GetPayload(context.Context, [8]byte) (*enginev1.ExecutionPayload, error) {
+	return nil, nil
+}
+
+func (*mockEngineService) ExchangeTransitionConfiguration(context.Context, *enginev1.TransitionConfiguration) error {
+	return nil
+}
+
+func (*mockEngineService) LatestExecutionBlock(context.Context) (*enginev1.ExecutionBlock, error) {
+	return nil, nil
+}
+
+func (m *mockEngineService) ExecutionBlockByHash(_ context.Context, hash common.Hash) (*enginev1.ExecutionBlock, error) {
+	blk, ok := m.blks[common.BytesToHash(hash.Bytes())]
+	if !ok {
+		return nil, errors.New("block not found")
+	}
+	return blk, nil
+}
--- a/beacon-chain/blockchain/mock_test.go
+++ b/beacon-chain/blockchain/mock_test.go
@@ -0,0 +1,50 @@
+package blockchain
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	testDB "github.com/prysmaticlabs/prysm/beacon-chain/db/testing"
+	"github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/protoarray"
+	"github.com/prysmaticlabs/prysm/beacon-chain/state"
+	"github.com/prysmaticlabs/prysm/beacon-chain/state/stategen"
+)
+
+func testServiceOptsWithDB(t *testing.T) []Option {
+	beaconDB := testDB.SetupDB(t)
+	fcs := protoarray.New(0, 0, [32]byte{'a'})
+	return []Option{
+		WithDatabase(beaconDB),
+		WithStateGen(stategen.New(beaconDB)),
+		WithForkChoiceStore(fcs),
+	}
+}
+
+// warning: only use these opts when you are certain there are no db calls
+// in your code path. this is a lightweight way to satisfy the stategen/beacondb
+// initialization requirements w/o the overhead of db init.
+func testServiceOptsNoDB() []Option {
+	return []Option{
+		withStateBalanceCache(satisfactoryStateBalanceCache()),
+	}
+}
+
+type mockStateByRooter struct {
+	state state.BeaconState
+	err   error
+}
+
+var _ stateByRooter = &mockStateByRooter{}
+
+func (m mockStateByRooter) StateByRoot(_ context.Context, _ [32]byte) (state.BeaconState, error) {
+	return m.state, m.err
+}
+
+// returns an instance of the state balance cache that can be used
+// to satisfy the requirement for one in NewService, but which will
+// always return an error if used.
+func satisfactoryStateBalanceCache() *stateBalanceCache {
+	err := errors.New("satisfactoryStateBalanceCache doesn't perform real caching")
+	return &stateBalanceCache{stateGen: mockStateByRooter{err: err}}
+}
--- a/beacon-chain/blockchain/new_slot.go
+++ b/beacon-chain/blockchain/new_slot.go
@@ -0,0 +1,72 @@
+package blockchain
+
+import (
+	"bytes"
+	"context"
+
+	"github.com/pkg/errors"
+	types "github.com/prysmaticlabs/eth2-types"
+	"github.com/prysmaticlabs/prysm/time/slots"
+)
+
+// NewSlot mimics the implementation of `on_tick` in fork choice consensus spec.
+// It resets the proposer boost root in fork choice, and it updates store's justified checkpoint
+// if a better checkpoint on the store's finalized checkpoint chain.
+// This should only be called at the start of every slot interval.
+//
+// Spec pseudocode definition:
+//    # Reset store.proposer_boost_root if this is a new slot
+//    if current_slot > previous_slot:
+//        store.proposer_boost_root = Root()
+//
+//    # Not a new epoch, return
+//    if not (current_slot > previous_slot and compute_slots_since_epoch_start(current_slot) == 0):
+//        return
+//
+//    # Update store.justified_checkpoint if a better checkpoint on the store.finalized_checkpoint chain
+//    if store.best_justified_checkpoint.epoch > store.justified_checkpoint.epoch:
+//        finalized_slot = compute_start_slot_at_epoch(store.finalized_checkpoint.epoch)
+//        ancestor_at_finalized_slot = get_ancestor(store, store.best_justified_checkpoint.root, finalized_slot)
+//        if ancestor_at_finalized_slot == store.finalized_checkpoint.root:
+//            store.justified_checkpoint = store.best_justified_checkpoint
+func (s *Service) NewSlot(ctx context.Context, slot types.Slot) error {
+
+	// Reset proposer boost root in fork choice.
+	if err := s.cfg.ForkChoiceStore.ResetBoostedProposerRoot(ctx); err != nil {
+		return errors.Wrap(err, "could not reset boosted proposer root in fork choice")
+	}
+
+	// Return if it's not a new epoch.
+	if !slots.IsEpochStart(slot) {
+		return nil
+	}
+
+	// Update store.justified_checkpoint if a better checkpoint on the store.finalized_checkpoint chain
+	bj := s.store.BestJustifiedCheckpt()
+	if bj == nil {
+		return errNilBestJustifiedInStore
+	}
+	j := s.store.JustifiedCheckpt()
+	if j == nil {
+		return errNilJustifiedInStore
+	}
+	f := s.store.FinalizedCheckpt()
+	if f == nil {
+		return errNilFinalizedInStore
+	}
+	if bj.Epoch > j.Epoch {
+		finalizedSlot, err := slots.EpochStart(f.Epoch)
+		if err != nil {
+			return err
+		}
+		r, err := s.ancestor(ctx, bj.Root, finalizedSlot)
+		if err != nil {
+			return err
+		}
+		if bytes.Equal(r, f.Root) {
+			s.store.SetJustifiedCheckpt(bj)
+		}
+	}
+	return nil
+
+}
--- a/beacon-chain/blockchain/new_slot_test.go
+++ b/beacon-chain/blockchain/new_slot_test.go
@@ -0,0 +1,100 @@
+package blockchain
+
+import (
+	"context"
+	"testing"
+
+	types "github.com/prysmaticlabs/eth2-types"
+	"github.com/prysmaticlabs/prysm/beacon-chain/blockchain/store"
+	testDB "github.com/prysmaticlabs/prysm/beacon-chain/db/testing"
+	"github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/protoarray"
+	"github.com/prysmaticlabs/prysm/beacon-chain/state/stategen"
+	"github.com/prysmaticlabs/prysm/config/params"
+	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
+	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
+	"github.com/prysmaticlabs/prysm/testing/require"
+)
+
+func TestService_newSlot(t *testing.T) {
+	beaconDB := testDB.SetupDB(t)
+	fcs := protoarray.New(0, 0, [32]byte{})
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithStateGen(stategen.New(beaconDB)),
+		WithForkChoiceStore(fcs),
+	}
+	ctx := context.Background()
+
+	require.NoError(t, fcs.InsertOptimisticBlock(ctx, 0, [32]byte{}, [32]byte{}, [32]byte{}, 0, 0))        // genesis
+	require.NoError(t, fcs.InsertOptimisticBlock(ctx, 32, [32]byte{'a'}, [32]byte{}, [32]byte{}, 0, 0))    // finalized
+	require.NoError(t, fcs.InsertOptimisticBlock(ctx, 64, [32]byte{'b'}, [32]byte{'a'}, [32]byte{}, 0, 0)) // justified
+	require.NoError(t, fcs.InsertOptimisticBlock(ctx, 96, [32]byte{'c'}, [32]byte{'a'}, [32]byte{}, 0, 0)) // best justified
+	require.NoError(t, fcs.InsertOptimisticBlock(ctx, 97, [32]byte{'d'}, [32]byte{}, [32]byte{}, 0, 0))    // bad
+
+	type args struct {
+		slot          types.Slot
+		finalized     *ethpb.Checkpoint
+		justified     *ethpb.Checkpoint
+		bestJustified *ethpb.Checkpoint
+		shouldEqual   bool
+	}
+	tests := []struct {
+		name string
+		args args
+	}{
+		{
+			name: "Not epoch boundary. No change",
+			args: args{
+				slot:          params.BeaconConfig().SlotsPerEpoch + 1,
+				finalized:     &ethpb.Checkpoint{Epoch: 1, Root: bytesutil.PadTo([]byte{'a'}, 32)},
+				justified:     &ethpb.Checkpoint{Epoch: 2, Root: bytesutil.PadTo([]byte{'b'}, 32)},
+				bestJustified: &ethpb.Checkpoint{Epoch: 3, Root: bytesutil.PadTo([]byte{'c'}, 32)},
+				shouldEqual:   false,
+			},
+		},
+		{
+			name: "Justified higher than best justified. No change",
+			args: args{
+				slot:          params.BeaconConfig().SlotsPerEpoch,
+				finalized:     &ethpb.Checkpoint{Epoch: 1, Root: bytesutil.PadTo([]byte{'a'}, 32)},
+				justified:     &ethpb.Checkpoint{Epoch: 3, Root: bytesutil.PadTo([]byte{'b'}, 32)},
+				bestJustified: &ethpb.Checkpoint{Epoch: 2, Root: bytesutil.PadTo([]byte{'c'}, 32)},
+				shouldEqual:   false,
+			},
+		},
+		{
+			name: "Best justified not on the same chain as finalized. No change",
+			args: args{
+				slot:          params.BeaconConfig().SlotsPerEpoch,
+				finalized:     &ethpb.Checkpoint{Epoch: 1, Root: bytesutil.PadTo([]byte{'a'}, 32)},
+				justified:     &ethpb.Checkpoint{Epoch: 2, Root: bytesutil.PadTo([]byte{'b'}, 32)},
+				bestJustified: &ethpb.Checkpoint{Epoch: 3, Root: bytesutil.PadTo([]byte{'d'}, 32)},
+				shouldEqual:   false,
+			},
+		},
+		{
+			name: "Best justified on the same chain as finalized. Yes change",
+			args: args{
+				slot:          params.BeaconConfig().SlotsPerEpoch,
+				finalized:     &ethpb.Checkpoint{Epoch: 1, Root: bytesutil.PadTo([]byte{'a'}, 32)},
+				justified:     &ethpb.Checkpoint{Epoch: 2, Root: bytesutil.PadTo([]byte{'b'}, 32)},
+				bestJustified: &ethpb.Checkpoint{Epoch: 3, Root: bytesutil.PadTo([]byte{'c'}, 32)},
+				shouldEqual:   true,
+			},
+		},
+	}
+	for _, test := range tests {
+		service, err := NewService(ctx, opts...)
+		require.NoError(t, err)
+		store := store.New(test.args.justified, test.args.finalized)
+		store.SetBestJustifiedCheckpt(test.args.bestJustified)
+		service.store = store
+
+		require.NoError(t, service.NewSlot(ctx, test.args.slot))
+		if test.args.shouldEqual {
+			require.DeepSSZEqual(t, service.store.BestJustifiedCheckpt(), service.store.JustifiedCheckpt())
+		} else {
+			require.DeepNotSSZEqual(t, service.store.BestJustifiedCheckpt(), service.store.JustifiedCheckpt())
+		}
+	}
+}
--- a/beacon-chain/blockchain/optimistic_sync.go
+++ b/beacon-chain/blockchain/optimistic_sync.go
@@ -0,0 +1,189 @@
+package blockchain
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/pkg/errors"
+	"github.com/prysmaticlabs/prysm/beacon-chain/core/blocks"
+	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
+	v1 "github.com/prysmaticlabs/prysm/beacon-chain/powchain/engine-api-client/v1"
+	"github.com/prysmaticlabs/prysm/config/params"
+	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
+	enginev1 "github.com/prysmaticlabs/prysm/proto/engine/v1"
+	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
+	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/block"
+	"github.com/sirupsen/logrus"
+	"go.opencensus.io/trace"
+)
+
+// notifyForkchoiceUpdate signals execution engine the fork choice updates. Execution engine should:
+// 1. Re-organizes the execution payload chain and corresponding state to make head_block_hash the head.
+// 2. Applies finality to the execution state: it irreversibly persists the chain of all execution payloads and corresponding state, up to and including finalized_block_hash.
+func (s *Service) notifyForkchoiceUpdate(ctx context.Context, headBlk block.BeaconBlock, headRoot [32]byte, finalizedRoot [32]byte) (*enginev1.PayloadIDBytes, error) {
+	ctx, span := trace.StartSpan(ctx, "blockChain.notifyForkchoiceUpdate")
+	defer span.End()
+
+	if headBlk == nil || headBlk.IsNil() || headBlk.Body().IsNil() {
+		return nil, errors.New("nil head block")
+	}
+	// Must not call fork choice updated until the transition conditions are met on the Pow network.
+	isExecutionBlk, err := blocks.IsExecutionBlock(headBlk.Body())
+	if err != nil {
+		return nil, errors.Wrap(err, "could not determine if block is execution block")
+	}
+	if !isExecutionBlk {
+		return nil, nil
+	}
+	headPayload, err := headBlk.Body().ExecutionPayload()
+	if err != nil {
+		return nil, errors.Wrap(err, "could not get execution payload")
+	}
+	finalizedBlock, err := s.cfg.BeaconDB.Block(ctx, s.ensureRootNotZeros(finalizedRoot))
+	if err != nil {
+		return nil, errors.Wrap(err, "could not get finalized block")
+	}
+	var finalizedHash []byte
+	if blocks.IsPreBellatrixVersion(finalizedBlock.Block().Version()) {
+		finalizedHash = params.BeaconConfig().ZeroHash[:]
+	} else {
+		payload, err := finalizedBlock.Block().Body().ExecutionPayload()
+		if err != nil {
+			return nil, errors.Wrap(err, "could not get finalized block execution payload")
+		}
+		finalizedHash = payload.BlockHash
+	}
+
+	fcs := &enginev1.ForkchoiceState{
+		HeadBlockHash:      headPayload.BlockHash,
+		SafeBlockHash:      headPayload.BlockHash,
+		FinalizedBlockHash: finalizedHash,
+	}
+
+	// payload attribute is only required when requesting payload, here we are just updating fork choice, so it is nil.
+	payloadID, _, err := s.cfg.ExecutionEngineCaller.ForkchoiceUpdated(ctx, fcs, nil /*payload attribute*/)
+	if err != nil {
+		switch err {
+		case v1.ErrAcceptedSyncingPayloadStatus:
+			log.WithFields(logrus.Fields{
+				"headSlot":      headBlk.Slot(),
+				"headHash":      fmt.Sprintf("%#x", bytesutil.Trunc(headPayload.BlockHash)),
+				"finalizedHash": fmt.Sprintf("%#x", bytesutil.Trunc(finalizedHash)),
+			}).Info("Called fork choice updated with optimistic block")
+			return payloadID, nil
+		default:
+			return nil, errors.Wrap(err, "could not notify forkchoice update from execution engine")
+		}
+	}
+	if err := s.cfg.ForkChoiceStore.SetOptimisticToValid(ctx, headRoot); err != nil {
+		return nil, errors.Wrap(err, "could not set block to valid")
+	}
+	return payloadID, nil
+}
+
+// notifyForkchoiceUpdate signals execution engine on a new payload
+func (s *Service) notifyNewPayload(ctx context.Context, preStateVersion, postStateVersion int,
+	preStateHeader, postStateHeader *ethpb.ExecutionPayloadHeader, blk block.SignedBeaconBlock, root [32]byte) error {
+	ctx, span := trace.StartSpan(ctx, "blockChain.notifyNewPayload")
+	defer span.End()
+
+	// Execution payload is only supported in Bellatrix and beyond. Pre
+	// merge blocks are never optimistic
+	if blocks.IsPreBellatrixVersion(postStateVersion) {
+		return s.cfg.ForkChoiceStore.SetOptimisticToValid(ctx, root)
+	}
+	if err := helpers.BeaconBlockIsNil(blk); err != nil {
+		return err
+	}
+	body := blk.Block().Body()
+	enabled, err := blocks.IsExecutionEnabledUsingHeader(postStateHeader, body)
+	if err != nil {
+		return errors.Wrap(err, "could not determine if execution is enabled")
+	}
+	if !enabled {
+		return s.cfg.ForkChoiceStore.SetOptimisticToValid(ctx, root)
+	}
+	payload, err := body.ExecutionPayload()
+	if err != nil {
+		return errors.Wrap(err, "could not get execution payload")
+	}
+	_, err = s.cfg.ExecutionEngineCaller.NewPayload(ctx, payload)
+	if err != nil {
+		switch err {
+		case v1.ErrAcceptedSyncingPayloadStatus:
+			log.WithFields(logrus.Fields{
+				"slot":      blk.Block().Slot(),
+				"blockHash": fmt.Sprintf("%#x", bytesutil.Trunc(payload.BlockHash)),
+			}).Info("Called new payload with optimistic block")
+			return nil
+		default:
+			return errors.Wrap(err, "could not validate execution payload from execution engine")
+		}
+	}
+
+	if err := s.cfg.ForkChoiceStore.SetOptimisticToValid(ctx, root); err != nil {
+		return errors.Wrap(err, "could not set optimistic status")
+	}
+
+	// During the transition event, the transition block should be verified for sanity.
+	if blocks.IsPreBellatrixVersion(preStateVersion) {
+		// Handle case where pre-state is Altair but block contains payload.
+		// To reach here, the block must have contained a valid payload.
+		return s.validateMergeBlock(ctx, blk)
+	}
+	atTransition, err := blocks.IsMergeTransitionBlockUsingPreStatePayloadHeader(preStateHeader, body)
+	if err != nil {
+		return errors.Wrap(err, "could not check if merge block is terminal")
+	}
+	if !atTransition {
+		return nil
+	}
+	return s.validateMergeBlock(ctx, blk)
+}
+
+// optimisticCandidateBlock returns true if this block can be optimistically synced.
+//
+// Spec pseudocode definition:
+// def is_optimistic_candidate_block(opt_store: OptimisticStore, current_slot: Slot, block: BeaconBlock) -> bool:
+//    if is_execution_block(opt_store.blocks[block.parent_root]):
+//        return True
+//
+//    justified_root = opt_store.block_states[opt_store.head_block_root].current_justified_checkpoint.root
+//    if is_execution_block(opt_store.blocks[justified_root]):
+//        return True
+//
+//    if block.slot + SAFE_SLOTS_TO_IMPORT_OPTIMISTICALLY <= current_slot:
+//        return True
+//
+//    return False
+func (s *Service) optimisticCandidateBlock(ctx context.Context, blk block.BeaconBlock) (bool, error) {
+	if blk.Slot()+params.BeaconConfig().SafeSlotsToImportOptimistically <= s.CurrentSlot() {
+		return true, nil
+	}
+
+	parent, err := s.cfg.BeaconDB.Block(ctx, bytesutil.ToBytes32(blk.ParentRoot()))
+	if err != nil {
+		return false, err
+	}
+	if parent == nil {
+		return false, errNilParentInDB
+	}
+
+	parentIsExecutionBlock, err := blocks.IsExecutionBlock(parent.Block().Body())
+	if err != nil {
+		return false, err
+	}
+	if parentIsExecutionBlock {
+		return true, nil
+	}
+
+	j := s.store.JustifiedCheckpt()
+	if j == nil {
+		return false, errNilJustifiedInStore
+	}
+	jBlock, err := s.cfg.BeaconDB.Block(ctx, bytesutil.ToBytes32(j.Root))
+	if err != nil {
+		return false, err
+	}
+	return blocks.IsExecutionBlock(jBlock.Block().Body())
+}
--- a/beacon-chain/blockchain/optimistic_sync_test.go
+++ b/beacon-chain/blockchain/optimistic_sync_test.go
@@ -0,0 +1,692 @@
+package blockchain
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/prysmaticlabs/prysm/beacon-chain/core/blocks"
+	testDB "github.com/prysmaticlabs/prysm/beacon-chain/db/testing"
+	"github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/protoarray"
+	engine "github.com/prysmaticlabs/prysm/beacon-chain/powchain/engine-api-client/v1"
+	"github.com/prysmaticlabs/prysm/beacon-chain/state"
+	"github.com/prysmaticlabs/prysm/beacon-chain/state/stategen"
+	fieldparams "github.com/prysmaticlabs/prysm/config/fieldparams"
+	"github.com/prysmaticlabs/prysm/config/params"
+	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
+	v1 "github.com/prysmaticlabs/prysm/proto/engine/v1"
+	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
+	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/block"
+	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/wrapper"
+	"github.com/prysmaticlabs/prysm/runtime/version"
+	"github.com/prysmaticlabs/prysm/testing/assert"
+	"github.com/prysmaticlabs/prysm/testing/require"
+	"github.com/prysmaticlabs/prysm/testing/util"
+	"github.com/prysmaticlabs/prysm/time/slots"
+)
+
+func Test_NotifyForkchoiceUpdate(t *testing.T) {
+	ctx := context.Background()
+	beaconDB := testDB.SetupDB(t)
+	altairBlk, err := wrapper.WrappedSignedBeaconBlock(util.NewBeaconBlockAltair())
+	require.NoError(t, err)
+	altairBlkRoot, err := altairBlk.Block().HashTreeRoot()
+	require.NoError(t, err)
+	bellatrixBlk, err := wrapper.WrappedSignedBeaconBlock(util.NewBeaconBlockBellatrix())
+	require.NoError(t, err)
+	bellatrixBlkRoot, err := bellatrixBlk.Block().HashTreeRoot()
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, altairBlk))
+	require.NoError(t, beaconDB.SaveBlock(ctx, bellatrixBlk))
+	fcs := protoarray.New(0, 0, [32]byte{'a'})
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithStateGen(stategen.New(beaconDB)),
+		WithForkChoiceStore(fcs),
+	}
+	service, err := NewService(ctx, opts...)
+	require.NoError(t, err)
+	require.NoError(t, fcs.InsertOptimisticBlock(ctx, 0, [32]byte{}, [32]byte{}, params.BeaconConfig().ZeroHash, 0, 0))
+
+	tests := []struct {
+		name             string
+		blk              block.BeaconBlock
+		finalizedRoot    [32]byte
+		newForkchoiceErr error
+		errString        string
+	}{
+		{
+			name:      "nil block",
+			errString: "nil head block",
+		},
+		{
+			name: "phase0 block",
+			blk: func() block.BeaconBlock {
+				b, err := wrapper.WrappedBeaconBlock(&ethpb.BeaconBlock{Body: &ethpb.BeaconBlockBody{}})
+				require.NoError(t, err)
+				return b
+			}(),
+		},
+		{
+			name: "altair block",
+			blk: func() block.BeaconBlock {
+				b, err := wrapper.WrappedBeaconBlock(&ethpb.BeaconBlockAltair{Body: &ethpb.BeaconBlockBodyAltair{}})
+				require.NoError(t, err)
+				return b
+			}(),
+		},
+		{
+			name: "not execution block",
+			blk: func() block.BeaconBlock {
+				b, err := wrapper.WrappedBeaconBlock(&ethpb.BeaconBlockBellatrix{
+					Body: &ethpb.BeaconBlockBodyBellatrix{
+						ExecutionPayload: &v1.ExecutionPayload{
+							ParentHash:    make([]byte, fieldparams.RootLength),
+							FeeRecipient:  make([]byte, fieldparams.FeeRecipientLength),
+							StateRoot:     make([]byte, fieldparams.RootLength),
+							ReceiptsRoot:  make([]byte, fieldparams.RootLength),
+							LogsBloom:     make([]byte, fieldparams.LogsBloomLength),
+							PrevRandao:    make([]byte, fieldparams.RootLength),
+							BaseFeePerGas: make([]byte, fieldparams.RootLength),
+							BlockHash:     make([]byte, fieldparams.RootLength),
+						},
+					},
+				})
+				require.NoError(t, err)
+				return b
+			}(),
+		},
+		{
+			name: "happy case: finalized root is altair block",
+			blk: func() block.BeaconBlock {
+				b, err := wrapper.WrappedBeaconBlock(&ethpb.BeaconBlockBellatrix{
+					Body: &ethpb.BeaconBlockBodyBellatrix{
+						ExecutionPayload: &v1.ExecutionPayload{},
+					},
+				})
+				require.NoError(t, err)
+				return b
+			}(),
+			finalizedRoot: altairBlkRoot,
+		},
+		{
+			name: "happy case: finalized root is bellatrix block",
+			blk: func() block.BeaconBlock {
+				b, err := wrapper.WrappedBeaconBlock(&ethpb.BeaconBlockBellatrix{
+					Body: &ethpb.BeaconBlockBodyBellatrix{
+						ExecutionPayload: &v1.ExecutionPayload{},
+					},
+				})
+				require.NoError(t, err)
+				return b
+			}(),
+			finalizedRoot: bellatrixBlkRoot,
+		},
+		{
+			name: "forkchoice updated with optimistic block",
+			blk: func() block.BeaconBlock {
+				b, err := wrapper.WrappedBeaconBlock(&ethpb.BeaconBlockBellatrix{
+					Body: &ethpb.BeaconBlockBodyBellatrix{
+						ExecutionPayload: &v1.ExecutionPayload{},
+					},
+				})
+				require.NoError(t, err)
+				return b
+			}(),
+			newForkchoiceErr: engine.ErrAcceptedSyncingPayloadStatus,
+			finalizedRoot:    bellatrixBlkRoot,
+		},
+		{
+			name: "forkchoice updated with invalid block",
+			blk: func() block.BeaconBlock {
+				b, err := wrapper.WrappedBeaconBlock(&ethpb.BeaconBlockBellatrix{
+					Body: &ethpb.BeaconBlockBodyBellatrix{
+						ExecutionPayload: &v1.ExecutionPayload{},
+					},
+				})
+				require.NoError(t, err)
+				return b
+			}(),
+			newForkchoiceErr: engine.ErrInvalidPayloadStatus,
+			finalizedRoot:    bellatrixBlkRoot,
+			errString:        "could not notify forkchoice update from execution engine: payload status is INVALID",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			engine := &mockEngineService{forkchoiceError: tt.newForkchoiceErr}
+			service.cfg.ExecutionEngineCaller = engine
+			_, err := service.notifyForkchoiceUpdate(ctx, tt.blk, service.headRoot(), tt.finalizedRoot)
+			if tt.errString != "" {
+				require.ErrorContains(t, tt.errString, err)
+			} else {
+				require.NoError(t, err)
+			}
+		})
+	}
+}
+
+func Test_NotifyNewPayload(t *testing.T) {
+	cfg := params.BeaconConfig()
+	cfg.TerminalTotalDifficulty = "2"
+	params.OverrideBeaconConfig(cfg)
+
+	ctx := context.Background()
+	beaconDB := testDB.SetupDB(t)
+	fcs := protoarray.New(0, 0, [32]byte{'a'})
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithStateGen(stategen.New(beaconDB)),
+		WithForkChoiceStore(fcs),
+	}
+	phase0State, _ := util.DeterministicGenesisState(t, 1)
+	altairState, _ := util.DeterministicGenesisStateAltair(t, 1)
+	bellatrixState, _ := util.DeterministicGenesisStateBellatrix(t, 2)
+	blk := &ethpb.SignedBeaconBlockBellatrix{
+		Block: &ethpb.BeaconBlockBellatrix{
+			Body: &ethpb.BeaconBlockBodyBellatrix{
+				ExecutionPayload: &v1.ExecutionPayload{},
+			},
+		},
+	}
+	a := &ethpb.SignedBeaconBlockAltair{
+		Block: &ethpb.BeaconBlockAltair{
+			Body: &ethpb.BeaconBlockBodyAltair{},
+		},
+	}
+	altairBlk, err := wrapper.WrappedSignedBeaconBlock(a)
+	require.NoError(t, err)
+	bellatrixBlk, err := wrapper.WrappedSignedBeaconBlock(blk)
+	require.NoError(t, err)
+	service, err := NewService(ctx, opts...)
+	require.NoError(t, err)
+
+	tests := []struct {
+		name          string
+		preState      state.BeaconState
+		postState     state.BeaconState
+		blk           block.SignedBeaconBlock
+		newPayloadErr error
+		errString     string
+	}{
+		{
+			name:      "phase 0 post state",
+			postState: phase0State,
+			preState:  phase0State,
+		},
+		{
+			name:      "altair post state",
+			postState: altairState,
+			preState:  altairState,
+		},
+		{
+			name:      "nil beacon block",
+			postState: bellatrixState,
+			preState:  bellatrixState,
+			errString: "signed beacon block can't be nil",
+		},
+		{
+			name:          "new payload with optimistic block",
+			postState:     bellatrixState,
+			preState:      bellatrixState,
+			blk:           bellatrixBlk,
+			newPayloadErr: engine.ErrAcceptedSyncingPayloadStatus,
+		},
+		{
+			name:          "new payload with invalid block",
+			postState:     bellatrixState,
+			preState:      bellatrixState,
+			blk:           bellatrixBlk,
+			newPayloadErr: engine.ErrInvalidPayloadStatus,
+			errString:     "could not validate execution payload from execution engine: payload status is INVALID",
+		},
+		{
+			name:      "altair pre state, altair block",
+			postState: bellatrixState,
+			preState:  altairState,
+			blk:       altairBlk,
+		},
+		{
+			name:      "altair pre state, happy case",
+			postState: bellatrixState,
+			preState:  altairState,
+			blk: func() block.SignedBeaconBlock {
+				blk := &ethpb.SignedBeaconBlockBellatrix{
+					Block: &ethpb.BeaconBlockBellatrix{
+						Body: &ethpb.BeaconBlockBodyBellatrix{
+							ExecutionPayload: &v1.ExecutionPayload{
+								ParentHash: bytesutil.PadTo([]byte{'a'}, fieldparams.RootLength),
+							},
+						},
+					},
+				}
+				b, err := wrapper.WrappedSignedBeaconBlock(blk)
+				require.NoError(t, err)
+				return b
+			}(),
+		},
+		{
+			name:      "could not get merge block",
+			postState: bellatrixState,
+			preState:  bellatrixState,
+			blk:       bellatrixBlk,
+			errString: "could not get merge block parent hash and total difficulty",
+		},
+		{
+			name:      "not at merge transition",
+			postState: bellatrixState,
+			preState:  bellatrixState,
+			blk: func() block.SignedBeaconBlock {
+				blk := &ethpb.SignedBeaconBlockBellatrix{
+					Block: &ethpb.BeaconBlockBellatrix{
+						Body: &ethpb.BeaconBlockBodyBellatrix{
+							ExecutionPayload: &v1.ExecutionPayload{
+								ParentHash:    make([]byte, fieldparams.RootLength),
+								FeeRecipient:  make([]byte, fieldparams.FeeRecipientLength),
+								StateRoot:     make([]byte, fieldparams.RootLength),
+								ReceiptsRoot:  make([]byte, fieldparams.RootLength),
+								LogsBloom:     make([]byte, fieldparams.LogsBloomLength),
+								PrevRandao:    make([]byte, fieldparams.RootLength),
+								BaseFeePerGas: make([]byte, fieldparams.RootLength),
+								BlockHash:     make([]byte, fieldparams.RootLength),
+							},
+						},
+					},
+				}
+				b, err := wrapper.WrappedSignedBeaconBlock(blk)
+				require.NoError(t, err)
+				return b
+			}(),
+		},
+		{
+			name:      "could not get merge block",
+			postState: bellatrixState,
+			preState:  bellatrixState,
+			blk:       bellatrixBlk,
+			errString: "could not get merge block parent hash and total difficulty",
+		},
+		{
+			name:      "happy case",
+			postState: bellatrixState,
+			preState:  bellatrixState,
+			blk: func() block.SignedBeaconBlock {
+				blk := &ethpb.SignedBeaconBlockBellatrix{
+					Block: &ethpb.BeaconBlockBellatrix{
+						Body: &ethpb.BeaconBlockBodyBellatrix{
+							ExecutionPayload: &v1.ExecutionPayload{
+								ParentHash: bytesutil.PadTo([]byte{'a'}, fieldparams.RootLength),
+							},
+						},
+					},
+				}
+				b, err := wrapper.WrappedSignedBeaconBlock(blk)
+				require.NoError(t, err)
+				return b
+			}(),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			engine := &mockEngineService{newPayloadError: tt.newPayloadErr, blks: map[[32]byte]*v1.ExecutionBlock{}}
+			engine.blks[[32]byte{'a'}] = &v1.ExecutionBlock{
+				ParentHash:      bytesutil.PadTo([]byte{'b'}, fieldparams.RootLength),
+				TotalDifficulty: "0x2",
+			}
+			engine.blks[[32]byte{'b'}] = &v1.ExecutionBlock{
+				ParentHash:      bytesutil.PadTo([]byte{'3'}, fieldparams.RootLength),
+				TotalDifficulty: "0x1",
+			}
+			service.cfg.ExecutionEngineCaller = engine
+			var payload *ethpb.ExecutionPayloadHeader
+			if tt.preState.Version() == version.Bellatrix {
+				payload, err = tt.preState.LatestExecutionPayloadHeader()
+				require.NoError(t, err)
+			}
+			root := [32]byte{'a'}
+			require.NoError(t, service.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 0, root, root, params.BeaconConfig().ZeroHash, 0, 0))
+			postVersion, postHeader, err := getStateVersionAndPayload(tt.postState)
+			require.NoError(t, err)
+			err = service.notifyNewPayload(ctx, tt.preState.Version(), postVersion, payload, postHeader, tt.blk, root)
+			if tt.errString != "" {
+				require.ErrorContains(t, tt.errString, err)
+			} else {
+				require.NoError(t, err)
+			}
+		})
+	}
+}
+
+func Test_NotifyNewPayload_SetOptimisticToValid(t *testing.T) {
+	cfg := params.BeaconConfig()
+	cfg.TerminalTotalDifficulty = "2"
+	params.OverrideBeaconConfig(cfg)
+	ctx := context.Background()
+	beaconDB := testDB.SetupDB(t)
+	fcs := protoarray.New(0, 0, [32]byte{'a'})
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithStateGen(stategen.New(beaconDB)),
+		WithForkChoiceStore(fcs),
+	}
+	bellatrixState, _ := util.DeterministicGenesisStateBellatrix(t, 2)
+	blk := &ethpb.SignedBeaconBlockBellatrix{
+		Block: &ethpb.BeaconBlockBellatrix{
+			Body: &ethpb.BeaconBlockBodyBellatrix{
+				ExecutionPayload: &v1.ExecutionPayload{
+					ParentHash: bytesutil.PadTo([]byte{'a'}, fieldparams.RootLength),
+				},
+			},
+		},
+	}
+	bellatrixBlk, err := wrapper.WrappedSignedBeaconBlock(blk)
+	require.NoError(t, err)
+	service, err := NewService(ctx, opts...)
+	require.NoError(t, err)
+	engine := &mockEngineService{blks: map[[32]byte]*v1.ExecutionBlock{}}
+	engine.blks[[32]byte{'a'}] = &v1.ExecutionBlock{
+		ParentHash:      bytesutil.PadTo([]byte{'b'}, fieldparams.RootLength),
+		TotalDifficulty: "0x2",
+	}
+	engine.blks[[32]byte{'b'}] = &v1.ExecutionBlock{
+		ParentHash:      bytesutil.PadTo([]byte{'3'}, fieldparams.RootLength),
+		TotalDifficulty: "0x1",
+	}
+	service.cfg.ExecutionEngineCaller = engine
+	payload, err := bellatrixState.LatestExecutionPayloadHeader()
+	require.NoError(t, err)
+	root := [32]byte{'c'}
+	require.NoError(t, service.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 1, root, [32]byte{'a'}, params.BeaconConfig().ZeroHash, 0, 0))
+	postVersion, postHeader, err := getStateVersionAndPayload(bellatrixState)
+	require.NoError(t, err)
+	err = service.notifyNewPayload(ctx, bellatrixState.Version(), postVersion, payload, postHeader, bellatrixBlk, root)
+	require.NoError(t, err)
+	optimistic, err := service.IsOptimisticForRoot(ctx, root)
+	require.NoError(t, err)
+	require.Equal(t, false, optimistic)
+}
+
+func Test_IsOptimisticCandidateBlock(t *testing.T) {
+	params.SetupTestConfigCleanup(t)
+	params.OverrideBeaconConfig(params.MainnetConfig())
+
+	ctx := context.Background()
+	beaconDB := testDB.SetupDB(t)
+	fcs := protoarray.New(0, 0, [32]byte{'a'})
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithStateGen(stategen.New(beaconDB)),
+		WithForkChoiceStore(fcs),
+	}
+
+	service, err := NewService(ctx, opts...)
+	require.NoError(t, err)
+
+	params.BeaconConfig().SafeSlotsToImportOptimistically = 128
+	service.genesisTime = time.Now().Add(-time.Second * 12 * 2 * 128)
+
+	parentBlk := util.NewBeaconBlockBellatrix()
+	wrappedParentBlock, err := wrapper.WrappedSignedBeaconBlock(parentBlk)
+	require.NoError(t, err)
+	parentRoot, err := wrappedParentBlock.Block().HashTreeRoot()
+	require.NoError(t, err)
+
+	tests := []struct {
+		name      string
+		blk       block.BeaconBlock
+		justified block.SignedBeaconBlock
+		want      bool
+	}{
+		{
+			name: "deep block",
+			blk: func(tt *testing.T) block.BeaconBlock {
+				blk := util.NewBeaconBlockBellatrix()
+				blk.Block.Slot = 1
+				blk.Block.ParentRoot = parentRoot[:]
+				wr, err := wrapper.WrappedBellatrixBeaconBlock(blk.Block)
+				require.NoError(tt, err)
+				return wr
+			}(t),
+			justified: func(tt *testing.T) block.SignedBeaconBlock {
+				blk := util.NewBeaconBlockBellatrix()
+				blk.Block.Slot = 32
+				blk.Block.ParentRoot = parentRoot[:]
+				wr, err := wrapper.WrappedSignedBeaconBlock(blk)
+				require.NoError(tt, err)
+				return wr
+			}(t),
+			want: true,
+		},
+		{
+			name: "shallow block, Altair justified chkpt",
+			blk: func(tt *testing.T) block.BeaconBlock {
+				blk := util.NewBeaconBlockAltair()
+				blk.Block.Slot = 200
+				blk.Block.ParentRoot = parentRoot[:]
+				wr, err := wrapper.WrappedAltairBeaconBlock(blk.Block)
+				require.NoError(tt, err)
+				return wr
+			}(t),
+			justified: func(tt *testing.T) block.SignedBeaconBlock {
+				blk := util.NewBeaconBlockAltair()
+				blk.Block.Slot = 32
+				blk.Block.ParentRoot = parentRoot[:]
+				wr, err := wrapper.WrappedSignedBeaconBlock(blk)
+				require.NoError(tt, err)
+				return wr
+			}(t),
+			want: false,
+		},
+		{
+			name: "shallow block, Bellatrix justified chkpt without execution",
+			blk: func(tt *testing.T) block.BeaconBlock {
+				blk := util.NewBeaconBlockBellatrix()
+				blk.Block.Slot = 200
+				blk.Block.ParentRoot = parentRoot[:]
+				wr, err := wrapper.WrappedBellatrixBeaconBlock(blk.Block)
+				require.NoError(tt, err)
+				return wr
+			}(t),
+			justified: func(tt *testing.T) block.SignedBeaconBlock {
+				blk := util.NewBeaconBlockBellatrix()
+				blk.Block.Slot = 32
+				blk.Block.ParentRoot = parentRoot[:]
+				wr, err := wrapper.WrappedSignedBeaconBlock(blk)
+				require.NoError(tt, err)
+				return wr
+			}(t),
+			want: false,
+		},
+		{
+			name: "shallow block, execution enabled justified chkpt",
+			blk: func(tt *testing.T) block.BeaconBlock {
+				blk := util.NewBeaconBlockBellatrix()
+				blk.Block.Slot = 200
+				blk.Block.ParentRoot = parentRoot[:]
+				wr, err := wrapper.WrappedBellatrixBeaconBlock(blk.Block)
+				require.NoError(tt, err)
+				return wr
+			}(t),
+			justified: func(tt *testing.T) block.SignedBeaconBlock {
+				blk := util.NewBeaconBlockBellatrix()
+				blk.Block.Slot = 32
+				blk.Block.ParentRoot = parentRoot[:]
+				blk.Block.Body.ExecutionPayload.ParentHash = bytesutil.PadTo([]byte{'a'}, fieldparams.RootLength)
+				blk.Block.Body.ExecutionPayload.FeeRecipient = bytesutil.PadTo([]byte{'a'}, fieldparams.FeeRecipientLength)
+				blk.Block.Body.ExecutionPayload.StateRoot = bytesutil.PadTo([]byte{'a'}, fieldparams.RootLength)
+				blk.Block.Body.ExecutionPayload.ReceiptsRoot = bytesutil.PadTo([]byte{'a'}, fieldparams.RootLength)
+				blk.Block.Body.ExecutionPayload.LogsBloom = bytesutil.PadTo([]byte{'a'}, fieldparams.LogsBloomLength)
+				blk.Block.Body.ExecutionPayload.PrevRandao = bytesutil.PadTo([]byte{'a'}, fieldparams.RootLength)
+				blk.Block.Body.ExecutionPayload.BaseFeePerGas = bytesutil.PadTo([]byte{'a'}, fieldparams.RootLength)
+				blk.Block.Body.ExecutionPayload.BlockHash = bytesutil.PadTo([]byte{'a'}, fieldparams.RootLength)
+				wr, err := wrapper.WrappedSignedBeaconBlock(blk)
+				require.NoError(tt, err)
+				return wr
+			}(t),
+			want: true,
+		},
+	}
+	for _, tt := range tests {
+		jroot, err := tt.justified.Block().HashTreeRoot()
+		require.NoError(t, err)
+		require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, tt.justified))
+		service.store.SetJustifiedCheckpt(
+			&ethpb.Checkpoint{
+				Root:  jroot[:],
+				Epoch: slots.ToEpoch(tt.justified.Block().Slot()),
+			})
+		require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wrappedParentBlock))
+
+		candidate, err := service.optimisticCandidateBlock(ctx, tt.blk)
+		require.NoError(t, err)
+		require.Equal(t, tt.want, candidate, tt.name)
+	}
+}
+
+func Test_IsOptimisticShallowExecutionParent(t *testing.T) {
+	params.SetupTestConfigCleanup(t)
+	params.OverrideBeaconConfig(params.MainnetConfig())
+
+	ctx := context.Background()
+	beaconDB := testDB.SetupDB(t)
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithStateGen(stategen.New(beaconDB)),
+	}
+
+	service, err := NewService(ctx, opts...)
+	require.NoError(t, err)
+
+	params.BeaconConfig().SafeSlotsToImportOptimistically = 128
+	service.genesisTime = time.Now().Add(-time.Second * 12 * 2 * 128)
+	payload := &v1.ExecutionPayload{
+		ParentHash:    make([]byte, 32),
+		FeeRecipient:  make([]byte, 20),
+		StateRoot:     make([]byte, 32),
+		ReceiptsRoot:  make([]byte, 32),
+		LogsBloom:     make([]byte, 256),
+		PrevRandao:    make([]byte, 32),
+		BaseFeePerGas: bytesutil.PadTo([]byte{1, 2, 3, 4}, fieldparams.RootLength),
+		BlockHash:     make([]byte, 32),
+		BlockNumber:   100,
+	}
+	body := &ethpb.BeaconBlockBodyBellatrix{ExecutionPayload: payload}
+	block := &ethpb.BeaconBlockBellatrix{Body: body, Slot: 200}
+	rawSigned := &ethpb.SignedBeaconBlockBellatrix{Block: block}
+	blk := util.HydrateSignedBeaconBlockBellatrix(rawSigned)
+	wr, err := wrapper.WrappedSignedBeaconBlock(blk)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wr))
+	blkRoot, err := wr.Block().HashTreeRoot()
+	require.NoError(t, err)
+
+	childBlock := util.NewBeaconBlockBellatrix()
+	childBlock.Block.ParentRoot = blkRoot[:]
+	// shallow block
+	childBlock.Block.Slot = 201
+	wrappedChild, err := wrapper.WrappedSignedBeaconBlock(childBlock)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wrappedChild))
+	candidate, err := service.optimisticCandidateBlock(ctx, wrappedChild.Block())
+	require.NoError(t, err)
+	require.Equal(t, true, candidate)
+}
+
+func Test_UpdateLastValidatedCheckpoint(t *testing.T) {
+	params.SetupTestConfigCleanup(t)
+	params.OverrideBeaconConfig(params.MainnetConfig())
+
+	ctx := context.Background()
+	beaconDB := testDB.SetupDB(t)
+	stateGen := stategen.New(beaconDB)
+	fcs := protoarray.New(0, 0, [32]byte{})
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithStateGen(stateGen),
+		WithForkChoiceStore(fcs),
+	}
+	service, err := NewService(ctx, opts...)
+	require.NoError(t, err)
+
+	genesisStateRoot := [32]byte{}
+	genesisBlk := blocks.NewGenesisBlock(genesisStateRoot[:])
+	wr, err := wrapper.WrappedSignedBeaconBlock(genesisBlk)
+	require.NoError(t, err)
+	assert.NoError(t, beaconDB.SaveBlock(ctx, wr))
+	genesisRoot, err := genesisBlk.Block.HashTreeRoot()
+	require.NoError(t, err)
+	assert.NoError(t, beaconDB.SaveGenesisBlockRoot(ctx, genesisRoot))
+	require.NoError(t, fcs.InsertOptimisticBlock(ctx, 0, genesisRoot, params.BeaconConfig().ZeroHash,
+		params.BeaconConfig().ZeroHash, 0, 0))
+	genesisSummary := &ethpb.StateSummary{
+		Root: genesisStateRoot[:],
+		Slot: 0,
+	}
+	require.NoError(t, beaconDB.SaveStateSummary(ctx, genesisSummary))
+
+	// Get last validated checkpoint
+	origCheckpoint, err := service.cfg.BeaconDB.LastValidatedCheckpoint(ctx)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveLastValidatedCheckpoint(ctx, origCheckpoint))
+
+	// Optimistic finalized checkpoint
+	blk := util.NewBeaconBlock()
+	blk.Block.Slot = 320
+	blk.Block.ParentRoot = genesisRoot[:]
+	wr, err = wrapper.WrappedSignedBeaconBlock(blk)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wr))
+	opRoot, err := blk.Block.HashTreeRoot()
+	require.NoError(t, err)
+
+	opCheckpoint := &ethpb.Checkpoint{
+		Root:  opRoot[:],
+		Epoch: 10,
+	}
+	opStateSummary := &ethpb.StateSummary{
+		Root: opRoot[:],
+		Slot: 320,
+	}
+	require.NoError(t, beaconDB.SaveStateSummary(ctx, opStateSummary))
+	require.NoError(t, fcs.InsertOptimisticBlock(ctx, 320, opRoot, genesisRoot,
+		params.BeaconConfig().ZeroHash, 10, 10))
+	assert.NoError(t, beaconDB.SaveGenesisBlockRoot(ctx, opRoot))
+	require.NoError(t, service.updateFinalized(ctx, opCheckpoint))
+	cp, err := service.cfg.BeaconDB.LastValidatedCheckpoint(ctx)
+	require.NoError(t, err)
+	require.DeepEqual(t, origCheckpoint.Root, cp.Root)
+	require.Equal(t, origCheckpoint.Epoch, cp.Epoch)
+
+	// Validated finalized checkpoint
+	blk = util.NewBeaconBlock()
+	blk.Block.Slot = 640
+	blk.Block.ParentRoot = opRoot[:]
+	wr, err = wrapper.WrappedSignedBeaconBlock(blk)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wr))
+	validRoot, err := blk.Block.HashTreeRoot()
+	require.NoError(t, err)
+
+	validCheckpoint := &ethpb.Checkpoint{
+		Root:  validRoot[:],
+		Epoch: 20,
+	}
+	validSummary := &ethpb.StateSummary{
+		Root: validRoot[:],
+		Slot: 640,
+	}
+	require.NoError(t, beaconDB.SaveStateSummary(ctx, validSummary))
+	require.NoError(t, fcs.InsertOptimisticBlock(ctx, 640, validRoot, params.BeaconConfig().ZeroHash,
+		params.BeaconConfig().ZeroHash, 20, 20))
+	require.NoError(t, fcs.SetOptimisticToValid(ctx, validRoot))
+	assert.NoError(t, beaconDB.SaveGenesisBlockRoot(ctx, validRoot))
+	require.NoError(t, service.updateFinalized(ctx, validCheckpoint))
+	cp, err = service.cfg.BeaconDB.LastValidatedCheckpoint(ctx)
+	require.NoError(t, err)
+
+	optimistic, err := service.IsOptimisticForRoot(ctx, validRoot)
+	require.NoError(t, err)
+	require.Equal(t, false, optimistic)
+	require.DeepEqual(t, validCheckpoint.Root, cp.Root)
+	require.Equal(t, validCheckpoint.Epoch, cp.Epoch)
+}
--- a/beacon-chain/blockchain/options.go
+++ b/beacon-chain/blockchain/options.go
@@ -0,0 +1,155 @@
+package blockchain
+
+import (
+	"github.com/prysmaticlabs/prysm/async/event"
+	"github.com/prysmaticlabs/prysm/beacon-chain/cache/depositcache"
+	statefeed "github.com/prysmaticlabs/prysm/beacon-chain/core/feed/state"
+	"github.com/prysmaticlabs/prysm/beacon-chain/db"
+	"github.com/prysmaticlabs/prysm/beacon-chain/forkchoice"
+	"github.com/prysmaticlabs/prysm/beacon-chain/operations/attestations"
+	"github.com/prysmaticlabs/prysm/beacon-chain/operations/slashings"
+	"github.com/prysmaticlabs/prysm/beacon-chain/operations/voluntaryexits"
+	"github.com/prysmaticlabs/prysm/beacon-chain/p2p"
+	"github.com/prysmaticlabs/prysm/beacon-chain/powchain"
+	enginev1 "github.com/prysmaticlabs/prysm/beacon-chain/powchain/engine-api-client/v1"
+	"github.com/prysmaticlabs/prysm/beacon-chain/state"
+	"github.com/prysmaticlabs/prysm/beacon-chain/state/stategen"
+	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
+)
+
+type Option func(s *Service) error
+
+// WithMaxGoroutines to control resource use of the blockchain service.
+func WithMaxGoroutines(x int) Option {
+	return func(s *Service) error {
+		s.cfg.MaxRoutines = x
+		return nil
+	}
+}
+
+// WithWeakSubjectivityCheckpoint for checkpoint sync.
+func WithWeakSubjectivityCheckpoint(c *ethpb.Checkpoint) Option {
+	return func(s *Service) error {
+		s.cfg.WeakSubjectivityCheckpt = c
+		return nil
+	}
+}
+
+// WithDatabase for head access.
+func WithDatabase(beaconDB db.HeadAccessDatabase) Option {
+	return func(s *Service) error {
+		s.cfg.BeaconDB = beaconDB
+		return nil
+	}
+}
+
+// WithChainStartFetcher to retrieve information about genesis.
+func WithChainStartFetcher(f powchain.ChainStartFetcher) Option {
+	return func(s *Service) error {
+		s.cfg.ChainStartFetcher = f
+		return nil
+	}
+}
+
+// WithExecutionEngineCaller to call execution engine.
+func WithExecutionEngineCaller(c enginev1.Caller) Option {
+	return func(s *Service) error {
+		s.cfg.ExecutionEngineCaller = c
+		return nil
+	}
+}
+
+// WithDepositCache for deposit lifecycle after chain inclusion.
+func WithDepositCache(c *depositcache.DepositCache) Option {
+	return func(s *Service) error {
+		s.cfg.DepositCache = c
+		return nil
+	}
+}
+
+// WithAttestationPool for attestation lifecycle after chain inclusion.
+func WithAttestationPool(p attestations.Pool) Option {
+	return func(s *Service) error {
+		s.cfg.AttPool = p
+		return nil
+	}
+}
+
+// WithExitPool for exits lifecycle after chain inclusion.
+func WithExitPool(p voluntaryexits.PoolManager) Option {
+	return func(s *Service) error {
+		s.cfg.ExitPool = p
+		return nil
+	}
+}
+
+// WithSlashingPool for slashings lifecycle after chain inclusion.
+func WithSlashingPool(p slashings.PoolManager) Option {
+	return func(s *Service) error {
+		s.cfg.SlashingPool = p
+		return nil
+	}
+}
+
+// WithP2PBroadcaster to broadcast messages after appropriate processing.
+func WithP2PBroadcaster(p p2p.Broadcaster) Option {
+	return func(s *Service) error {
+		s.cfg.P2p = p
+		return nil
+	}
+}
+
+// WithStateNotifier to notify an event feed of state processing.
+func WithStateNotifier(n statefeed.Notifier) Option {
+	return func(s *Service) error {
+		s.cfg.StateNotifier = n
+		return nil
+	}
+}
+
+// WithForkChoiceStore to update an optimized fork-choice representation.
+func WithForkChoiceStore(f forkchoice.ForkChoicer) Option {
+	return func(s *Service) error {
+		s.cfg.ForkChoiceStore = f
+		return nil
+	}
+}
+
+// WithAttestationService for dealing with attestation lifecycles.
+func WithAttestationService(srv *attestations.Service) Option {
+	return func(s *Service) error {
+		s.cfg.AttService = srv
+		return nil
+	}
+}
+
+// WithStateGen for managing state regeneration and replay.
+func WithStateGen(g *stategen.State) Option {
+	return func(s *Service) error {
+		s.cfg.StateGen = g
+		return nil
+	}
+}
+
+// WithSlasherAttestationsFeed to forward attestations into slasher if enabled.
+func WithSlasherAttestationsFeed(f *event.Feed) Option {
+	return func(s *Service) error {
+		s.cfg.SlasherAttestationsFeed = f
+		return nil
+	}
+}
+
+func withStateBalanceCache(c *stateBalanceCache) Option {
+	return func(s *Service) error {
+		s.justifiedBalances = c
+		return nil
+	}
+}
+
+// WithFinalizedStateAtStartUp to store finalized state at start up.
+func WithFinalizedStateAtStartUp(st state.BeaconState) Option {
+	return func(s *Service) error {
+		s.cfg.FinalizedStateAtStartUp = st
+		return nil
+	}
+}
--- a/beacon-chain/blockchain/pow_block.go
+++ b/beacon-chain/blockchain/pow_block.go
@@ -0,0 +1,141 @@
+package blockchain
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+	"github.com/holiman/uint256"
+	"github.com/pkg/errors"
+	types "github.com/prysmaticlabs/eth2-types"
+	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
+	"github.com/prysmaticlabs/prysm/config/params"
+	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
+	enginev1 "github.com/prysmaticlabs/prysm/proto/engine/v1"
+	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/block"
+	"github.com/prysmaticlabs/prysm/time/slots"
+	"github.com/sirupsen/logrus"
+)
+
+// validateMergeBlock validates terminal block hash in the event of manual overrides before checking for total difficulty.
+//
+// def validate_merge_block(block: BeaconBlock) -> None:
+//    if TERMINAL_BLOCK_HASH != Hash32():
+//        # If `TERMINAL_BLOCK_HASH` is used as an override, the activation epoch must be reached.
+//        assert compute_epoch_at_slot(block.slot) >= TERMINAL_BLOCK_HASH_ACTIVATION_EPOCH
+//        assert block.body.execution_payload.parent_hash == TERMINAL_BLOCK_HASH
+//        return
+//
+//    pow_block = get_pow_block(block.body.execution_payload.parent_hash)
+//    # Check if `pow_block` is available
+//    assert pow_block is not None
+//    pow_parent = get_pow_block(pow_block.parent_hash)
+//    # Check if `pow_parent` is available
+//    assert pow_parent is not None
+//    # Check if `pow_block` is a valid terminal PoW block
+//    assert is_valid_terminal_pow_block(pow_block, pow_parent)
+func (s *Service) validateMergeBlock(ctx context.Context, b block.SignedBeaconBlock) error {
+	if err := helpers.BeaconBlockIsNil(b); err != nil {
+		return err
+	}
+	payload, err := b.Block().Body().ExecutionPayload()
+	if err != nil {
+		return err
+	}
+	if payload == nil {
+		return errors.New("nil execution payload")
+	}
+	if err := validateTerminalBlockHash(b.Block().Slot(), payload); err != nil {
+		return errors.Wrap(err, "could not validate terminal block hash")
+	}
+	mergeBlockParentHash, mergeBlockTD, err := s.getBlkParentHashAndTD(ctx, payload.ParentHash)
+	if err != nil {
+		return errors.Wrap(err, "could not get merge block parent hash and total difficulty")
+	}
+	_, mergeBlockParentTD, err := s.getBlkParentHashAndTD(ctx, mergeBlockParentHash)
+	if err != nil {
+		return errors.Wrap(err, "could not get merge parent block total difficulty")
+	}
+	valid, err := validateTerminalBlockDifficulties(mergeBlockTD, mergeBlockParentTD)
+	if err != nil {
+		return err
+	}
+	if !valid {
+		return fmt.Errorf("invalid TTD, configTTD: %s, currentTTD: %s, parentTTD: %s",
+			params.BeaconConfig().TerminalTotalDifficulty, mergeBlockTD, mergeBlockParentTD)
+	}
+
+	log.WithFields(logrus.Fields{
+		"slot":                            b.Block().Slot(),
+		"mergeBlockHash":                  common.BytesToHash(payload.ParentHash).String(),
+		"mergeBlockParentHash":            common.BytesToHash(mergeBlockParentHash).String(),
+		"terminalTotalDifficulty":         params.BeaconConfig().TerminalTotalDifficulty,
+		"mergeBlockTotalDifficulty":       mergeBlockTD,
+		"mergeBlockParentTotalDifficulty": mergeBlockParentTD,
+	}).Info("Validated terminal block")
+
+	return nil
+}
+
+// getBlkParentHashAndTD retrieves the parent hash and total difficulty of the given block.
+func (s *Service) getBlkParentHashAndTD(ctx context.Context, blkHash []byte) ([]byte, *uint256.Int, error) {
+	blk, err := s.cfg.ExecutionEngineCaller.ExecutionBlockByHash(ctx, common.BytesToHash(blkHash))
+	if err != nil {
+		return nil, nil, errors.Wrap(err, "could not get pow block")
+	}
+	if blk == nil {
+		return nil, nil, errors.New("pow block is nil")
+	}
+	blkTDBig, err := hexutil.DecodeBig(blk.TotalDifficulty)
+	if err != nil {
+		return nil, nil, errors.Wrap(err, "could not decode merge block total difficulty")
+	}
+	blkTDUint256, overflows := uint256.FromBig(blkTDBig)
+	if overflows {
+		return nil, nil, errors.New("total difficulty overflows")
+	}
+	return blk.ParentHash, blkTDUint256, nil
+}
+
+// validateTerminalBlockHash validates if the merge block is a valid terminal PoW block.
+// spec code:
+// if TERMINAL_BLOCK_HASH != Hash32():
+//        # If `TERMINAL_BLOCK_HASH` is used as an override, the activation epoch must be reached.
+//        assert compute_epoch_at_slot(block.slot) >= TERMINAL_BLOCK_HASH_ACTIVATION_EPOCH
+//        assert block.body.execution_payload.parent_hash == TERMINAL_BLOCK_HASH
+//        return
+func validateTerminalBlockHash(blkSlot types.Slot, payload *enginev1.ExecutionPayload) error {
+	if bytesutil.ToBytes32(params.BeaconConfig().TerminalBlockHash.Bytes()) == [32]byte{} {
+		return nil
+	}
+	if params.BeaconConfig().TerminalBlockHashActivationEpoch > slots.ToEpoch(blkSlot) {
+		return errors.New("terminal block hash activation epoch not reached")
+	}
+	if !bytes.Equal(payload.ParentHash, params.BeaconConfig().TerminalBlockHash.Bytes()) {
+		return errors.New("parent hash does not match terminal block hash")
+	}
+	return nil
+}
+
+// validateTerminalBlockDifficulties validates terminal pow block by comparing own total difficulty with parent's total difficulty.
+//
+// def is_valid_terminal_pow_block(block: PowBlock, parent: PowBlock) -> bool:
+//    is_total_difficulty_reached = block.total_difficulty >= TERMINAL_TOTAL_DIFFICULTY
+//    is_parent_total_difficulty_valid = parent.total_difficulty < TERMINAL_TOTAL_DIFFICULTY
+//    return is_total_difficulty_reached and is_parent_total_difficulty_valid
+func validateTerminalBlockDifficulties(currentDifficulty *uint256.Int, parentDifficulty *uint256.Int) (bool, error) {
+	b, ok := new(big.Int).SetString(params.BeaconConfig().TerminalTotalDifficulty, 10)
+	if !ok {
+		return false, errors.New("failed to parse terminal total difficulty")
+	}
+	ttd, of := uint256.FromBig(b)
+	if of {
+		return false, errors.New("overflow terminal total difficulty")
+	}
+	totalDifficultyReached := currentDifficulty.Cmp(ttd) >= 0
+	parentTotalDifficultyValid := ttd.Cmp(parentDifficulty) > 0
+	return totalDifficultyReached && parentTotalDifficultyValid, nil
+}
--- a/beacon-chain/blockchain/pow_block_test.go
+++ b/beacon-chain/blockchain/pow_block_test.go
@@ -0,0 +1,210 @@
+package blockchain
+
+import (
+	"context"
+	"fmt"
+	"math/big"
+	"testing"
+
+	"github.com/holiman/uint256"
+	testDB "github.com/prysmaticlabs/prysm/beacon-chain/db/testing"
+	"github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/protoarray"
+	"github.com/prysmaticlabs/prysm/beacon-chain/state/stategen"
+	fieldparams "github.com/prysmaticlabs/prysm/config/fieldparams"
+	"github.com/prysmaticlabs/prysm/config/params"
+	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
+	enginev1 "github.com/prysmaticlabs/prysm/proto/engine/v1"
+	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
+	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/wrapper"
+	"github.com/prysmaticlabs/prysm/testing/require"
+)
+
+func Test_validTerminalPowBlock(t *testing.T) {
+	tests := []struct {
+		name              string
+		currentDifficulty *uint256.Int
+		parentDifficulty  *uint256.Int
+		ttd               uint64
+		want              bool
+	}{
+		{
+			name:              "current > ttd, parent > ttd",
+			currentDifficulty: uint256.NewInt(2),
+			parentDifficulty:  uint256.NewInt(2),
+			ttd:               1,
+			want:              false,
+		},
+		{
+			name:              "current < ttd, parent < ttd",
+			currentDifficulty: uint256.NewInt(2),
+			parentDifficulty:  uint256.NewInt(2),
+			ttd:               3,
+			want:              false,
+		},
+		{
+			name:              "current == ttd, parent == ttd",
+			currentDifficulty: uint256.NewInt(2),
+			parentDifficulty:  uint256.NewInt(2),
+			ttd:               2,
+			want:              false,
+		},
+		{
+			name:              "current > ttd, parent == ttd",
+			currentDifficulty: uint256.NewInt(2),
+			parentDifficulty:  uint256.NewInt(1),
+			ttd:               1,
+			want:              false,
+		},
+		{
+			name:              "current == ttd, parent < ttd",
+			currentDifficulty: uint256.NewInt(2),
+			parentDifficulty:  uint256.NewInt(1),
+			ttd:               2,
+			want:              true,
+		},
+		{
+			name:              "current > ttd, parent < ttd",
+			currentDifficulty: uint256.NewInt(3),
+			parentDifficulty:  uint256.NewInt(1),
+			ttd:               2,
+			want:              true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			cfg := params.BeaconConfig()
+			cfg.TerminalTotalDifficulty = fmt.Sprint(tt.ttd)
+			params.OverrideBeaconConfig(cfg)
+			got, err := validateTerminalBlockDifficulties(tt.currentDifficulty, tt.parentDifficulty)
+			require.NoError(t, err)
+			if got != tt.want {
+				t.Errorf("validateTerminalBlockDifficulties() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_validTerminalPowBlockSpecConfig(t *testing.T) {
+	cfg := params.BeaconConfig()
+	cfg.TerminalTotalDifficulty = "115792089237316195423570985008687907853269984665640564039457584007913129638912"
+	params.OverrideBeaconConfig(cfg)
+
+	i, _ := new(big.Int).SetString("115792089237316195423570985008687907853269984665640564039457584007913129638912", 10)
+	current, of := uint256.FromBig(i)
+	require.Equal(t, of, false)
+	i, _ = new(big.Int).SetString("115792089237316195423570985008687907853269984665640564039457584007913129638911", 10)
+	parent, of := uint256.FromBig(i)
+	require.Equal(t, of, false)
+
+	got, err := validateTerminalBlockDifficulties(current, parent)
+	require.NoError(t, err)
+	require.Equal(t, true, got)
+}
+
+func Test_validateMergeBlock(t *testing.T) {
+	cfg := params.BeaconConfig()
+	cfg.TerminalTotalDifficulty = "2"
+	params.OverrideBeaconConfig(cfg)
+
+	ctx := context.Background()
+	beaconDB := testDB.SetupDB(t)
+	fcs := protoarray.New(0, 0, [32]byte{'a'})
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithStateGen(stategen.New(beaconDB)),
+		WithForkChoiceStore(fcs),
+	}
+	service, err := NewService(ctx, opts...)
+	require.NoError(t, err)
+
+	engine := &mockEngineService{blks: map[[32]byte]*enginev1.ExecutionBlock{}}
+	service.cfg.ExecutionEngineCaller = engine
+	engine.blks[[32]byte{'a'}] = &enginev1.ExecutionBlock{
+		ParentHash:      bytesutil.PadTo([]byte{'b'}, fieldparams.RootLength),
+		TotalDifficulty: "0x2",
+	}
+	engine.blks[[32]byte{'b'}] = &enginev1.ExecutionBlock{
+		ParentHash:      bytesutil.PadTo([]byte{'3'}, fieldparams.RootLength),
+		TotalDifficulty: "0x1",
+	}
+	blk := &ethpb.SignedBeaconBlockBellatrix{
+		Block: &ethpb.BeaconBlockBellatrix{
+			Slot: 1,
+			Body: &ethpb.BeaconBlockBodyBellatrix{
+				ExecutionPayload: &enginev1.ExecutionPayload{
+					ParentHash: bytesutil.PadTo([]byte{'a'}, fieldparams.RootLength),
+				},
+			},
+		},
+	}
+	b, err := wrapper.WrappedSignedBeaconBlock(blk)
+	require.NoError(t, err)
+	require.NoError(t, service.validateMergeBlock(ctx, b))
+
+	cfg.TerminalTotalDifficulty = "1"
+	params.OverrideBeaconConfig(cfg)
+	require.ErrorContains(t, "invalid TTD, configTTD: 1, currentTTD: 2, parentTTD: 1", service.validateMergeBlock(ctx, b))
+}
+
+func Test_getBlkParentHashAndTD(t *testing.T) {
+	ctx := context.Background()
+	beaconDB := testDB.SetupDB(t)
+	fcs := protoarray.New(0, 0, [32]byte{'a'})
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithStateGen(stategen.New(beaconDB)),
+		WithForkChoiceStore(fcs),
+	}
+	service, err := NewService(ctx, opts...)
+	require.NoError(t, err)
+
+	engine := &mockEngineService{blks: map[[32]byte]*enginev1.ExecutionBlock{}}
+	service.cfg.ExecutionEngineCaller = engine
+	h := [32]byte{'a'}
+	p := [32]byte{'b'}
+	td := "0x1"
+	engine.blks[h] = &enginev1.ExecutionBlock{
+		ParentHash:      p[:],
+		TotalDifficulty: td,
+	}
+	parentHash, totalDifficulty, err := service.getBlkParentHashAndTD(ctx, h[:])
+	require.NoError(t, err)
+	require.Equal(t, p, bytesutil.ToBytes32(parentHash))
+	require.Equal(t, td, totalDifficulty.String())
+
+	_, _, err = service.getBlkParentHashAndTD(ctx, []byte{'c'})
+	require.ErrorContains(t, "could not get pow block: block not found", err)
+
+	engine.blks[h] = nil
+	_, _, err = service.getBlkParentHashAndTD(ctx, h[:])
+	require.ErrorContains(t, "pow block is nil", err)
+
+	engine.blks[h] = &enginev1.ExecutionBlock{
+		ParentHash:      p[:],
+		TotalDifficulty: "1",
+	}
+	_, _, err = service.getBlkParentHashAndTD(ctx, h[:])
+	require.ErrorContains(t, "could not decode merge block total difficulty: hex string without 0x prefix", err)
+
+	engine.blks[h] = &enginev1.ExecutionBlock{
+		ParentHash:      p[:],
+		TotalDifficulty: "0XFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF",
+	}
+	_, _, err = service.getBlkParentHashAndTD(ctx, h[:])
+	require.ErrorContains(t, "could not decode merge block total difficulty: hex number > 256 bits", err)
+}
+
+func Test_validateTerminalBlockHash(t *testing.T) {
+	require.NoError(t, validateTerminalBlockHash(1, &enginev1.ExecutionPayload{}))
+
+	cfg := params.BeaconConfig()
+	cfg.TerminalBlockHash = [32]byte{0x01}
+	params.OverrideBeaconConfig(cfg)
+	require.ErrorContains(t, "terminal block hash activation epoch not reached", validateTerminalBlockHash(1, &enginev1.ExecutionPayload{}))
+
+	cfg.TerminalBlockHashActivationEpoch = 0
+	params.OverrideBeaconConfig(cfg)
+	require.ErrorContains(t, "parent hash does not match terminal block hash", validateTerminalBlockHash(1, &enginev1.ExecutionPayload{}))
+
+	require.NoError(t, validateTerminalBlockHash(1, &enginev1.ExecutionPayload{ParentHash: cfg.TerminalBlockHash.Bytes()}))
+}
--- a/beacon-chain/blockchain/process_attestation.go
+++ b/beacon-chain/blockchain/process_attestation.go
@@ -2,6 +2,7 @@ package blockchain

 import (
 	"context"
+	"time"

 	"github.com/pkg/errors"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
@@ -9,12 +10,11 @@ import (
 	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
 	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
 	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/attestation"
-	"github.com/prysmaticlabs/prysm/time"
 	"github.com/prysmaticlabs/prysm/time/slots"
 	"go.opencensus.io/trace"
 )

-// onAttestation is called whenever an attestation is received, verifies the attestation is valid and saves
+// OnAttestation is called whenever an attestation is received, verifies the attestation is valid and saves
 // it to the DB. As a stateless function, this does not hold nor delay attestation based on the spec descriptions.
 // The delay is handled by the caller in `processAttestations`.
 //
@@ -36,7 +36,7 @@ import (
 //
 //    # Update latest messages for attesting indices
 //    update_latest_messages(store, indexed_attestation.attesting_indices, attestation)
-func (s *Service) onAttestation(ctx context.Context, a *ethpb.Attestation) error {
+func (s *Service) OnAttestation(ctx context.Context, a *ethpb.Attestation) error {
 	ctx, span := trace.StartSpan(ctx, "blockChain.onAttestation")
 	defer span.End()

@@ -59,10 +59,10 @@ func (s *Service) onAttestation(ctx context.Context, a *ethpb.Attestation) error
 		return err
 	}

-	genesisTime := baseState.GenesisTime()
+	genesisTime := uint64(s.genesisTime.Unix())

 	// Verify attestation target is from current epoch or previous epoch.
-	if err := s.verifyAttTargetEpoch(ctx, genesisTime, uint64(time.Now().Unix()), tgt); err != nil {
+	if err := verifyAttTargetEpoch(ctx, genesisTime, uint64(time.Now().Unix()), tgt); err != nil {
 		return err
 	}

--- a/beacon-chain/blockchain/process_attestation_helpers.go
+++ b/beacon-chain/blockchain/process_attestation_helpers.go
@@ -42,11 +42,9 @@ func (s *Service) getAttPreState(ctx context.Context, c *ethpb.Checkpoint) (stat
 	if err != nil {
 		return nil, err
 	}
-	if epochStartSlot > baseState.Slot() {
-		baseState, err = transition.ProcessSlots(ctx, baseState, epochStartSlot)
-		if err != nil {
-			return nil, errors.Wrapf(err, "could not process slots up to epoch %d", c.Epoch)
-		}
+	baseState, err = transition.ProcessSlotsIfPossible(ctx, baseState, epochStartSlot)
+	if err != nil {
+		return nil, errors.Wrapf(err, "could not process slots up to epoch %d", c.Epoch)
 	}

 	// Sharing the same state across caches is perfectly fine here, the fetching
@@ -61,7 +59,7 @@ func (s *Service) getAttPreState(ctx context.Context, c *ethpb.Checkpoint) (stat
 }

 // verifyAttTargetEpoch validates attestation is from the current or previous epoch.
-func (s *Service) verifyAttTargetEpoch(_ context.Context, genesisTime, nowTime uint64, c *ethpb.Checkpoint) error {
+func verifyAttTargetEpoch(_ context.Context, genesisTime, nowTime uint64, c *ethpb.Checkpoint) error {
 	currentSlot := types.Slot((nowTime - genesisTime) / params.BeaconConfig().SecondsPerSlot)
 	currentEpoch := slots.ToEpoch(currentSlot)
 	var prevEpoch types.Epoch
@@ -87,7 +85,7 @@ func (s *Service) verifyBeaconBlock(ctx context.Context, data *ethpb.Attestation
 	if (b == nil || b.IsNil()) && s.hasInitSyncBlock(r) {
 		b = s.getInitSyncBlock(r)
 	}
-	if err := helpers.VerifyNilBeaconBlock(b); err != nil {
+	if err := helpers.BeaconBlockIsNil(b); err != nil {
 		return err
 	}
 	if b.Block().Slot() > data.Slot {
--- a/beacon-chain/blockchain/process_attestation_test.go
+++ b/beacon-chain/blockchain/process_attestation_test.go
@@ -3,12 +3,15 @@ package blockchain
 import (
 	"context"
 	"testing"
+	"time"

 	types "github.com/prysmaticlabs/eth2-types"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/transition"
 	testDB "github.com/prysmaticlabs/prysm/beacon-chain/db/testing"
+	doublylinkedtree "github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/doubly-linked-tree"
 	"github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/protoarray"
 	"github.com/prysmaticlabs/prysm/beacon-chain/state/stategen"
+	fieldparams "github.com/prysmaticlabs/prysm/config/fieldparams"
 	"github.com/prysmaticlabs/prysm/config/params"
 	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
 	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
@@ -16,20 +19,19 @@ import (
 	"github.com/prysmaticlabs/prysm/testing/assert"
 	"github.com/prysmaticlabs/prysm/testing/require"
 	"github.com/prysmaticlabs/prysm/testing/util"
-	"github.com/prysmaticlabs/prysm/time"
 	"github.com/prysmaticlabs/prysm/time/slots"
 )

-func TestStore_OnAttestation_ErrorConditions(t *testing.T) {
+func TestStore_OnAttestation_ErrorConditions_ProtoArray(t *testing.T) {
 	ctx := context.Background()
 	beaconDB := testDB.SetupDB(t)

-	cfg := &Config{
-		BeaconDB:        beaconDB,
-		ForkChoiceStore: protoarray.New(0, 0, [32]byte{}),
-		StateGen:        stategen.New(beaconDB),
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithForkChoiceStore(protoarray.New(0, 0, [32]byte{})),
+		WithStateGen(stategen.New(beaconDB)),
 	}
-	service, err := NewService(ctx, cfg)
+	service, err := NewService(ctx, opts...)
 	require.NoError(t, err)

 	_, err = blockTree1(t, beaconDB, []byte{'g'})
@@ -37,13 +39,17 @@ func TestStore_OnAttestation_ErrorConditions(t *testing.T) {

 	BlkWithOutState := util.NewBeaconBlock()
 	BlkWithOutState.Block.Slot = 0
-	require.NoError(t, beaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(BlkWithOutState)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(BlkWithOutState)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))
 	BlkWithOutStateRoot, err := BlkWithOutState.Block.HashTreeRoot()
 	require.NoError(t, err)

 	BlkWithStateBadAtt := util.NewBeaconBlock()
 	BlkWithStateBadAtt.Block.Slot = 1
-	require.NoError(t, beaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(BlkWithStateBadAtt)))
+	wsb, err = wrapper.WrappedSignedBeaconBlock(BlkWithStateBadAtt)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))
 	BlkWithStateBadAttRoot, err := BlkWithStateBadAtt.Block.HashTreeRoot()
 	require.NoError(t, err)

@@ -54,7 +60,9 @@ func TestStore_OnAttestation_ErrorConditions(t *testing.T) {

 	BlkWithValidState := util.NewBeaconBlock()
 	BlkWithValidState.Block.Slot = 2
-	require.NoError(t, beaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(BlkWithValidState)))
+	wsb, err = wrapper.WrappedSignedBeaconBlock(BlkWithValidState)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))

 	BlkWithValidStateRoot, err := BlkWithValidState.Block.HashTreeRoot()
 	require.NoError(t, err)
@@ -103,9 +111,9 @@ func TestStore_OnAttestation_ErrorConditions(t *testing.T) {
 			name: "process nil field (a.Target) in attestation",
 			a: &ethpb.Attestation{
 				Data: &ethpb.AttestationData{
-					BeaconBlockRoot: make([]byte, 32),
+					BeaconBlockRoot: make([]byte, fieldparams.RootLength),
 					Target:          nil,
-					Source:          &ethpb.Checkpoint{Root: make([]byte, 32)},
+					Source:          &ethpb.Checkpoint{Root: make([]byte, fieldparams.RootLength)},
 				},
 				AggregationBits: make([]byte, 1),
 				Signature:       make([]byte, 96),
@@ -116,7 +124,7 @@ func TestStore_OnAttestation_ErrorConditions(t *testing.T) {

 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			err := service.onAttestation(ctx, tt.a)
+			err := service.OnAttestation(ctx, tt.a)
 			if tt.wantedErr != "" {
 				assert.ErrorContains(t, tt.wantedErr, err)
 			} else {
@@ -126,19 +134,132 @@ func TestStore_OnAttestation_ErrorConditions(t *testing.T) {
 	}
 }

-func TestStore_OnAttestation_Ok(t *testing.T) {
+func TestStore_OnAttestation_ErrorConditions_DoublyLinkedTree(t *testing.T) {
 	ctx := context.Background()
 	beaconDB := testDB.SetupDB(t)

-	cfg := &Config{
-		BeaconDB:        beaconDB,
-		ForkChoiceStore: protoarray.New(0, 0, [32]byte{}),
-		StateGen:        stategen.New(beaconDB),
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithForkChoiceStore(doublylinkedtree.New(0, 0)),
+		WithStateGen(stategen.New(beaconDB)),
 	}
-	service, err := NewService(ctx, cfg)
+	service, err := NewService(ctx, opts...)
+	require.NoError(t, err)
+
+	_, err = blockTree1(t, beaconDB, []byte{'g'})
+	require.NoError(t, err)
+
+	BlkWithOutState := util.NewBeaconBlock()
+	BlkWithOutState.Block.Slot = 0
+	wsb, err := wrapper.WrappedSignedBeaconBlock(BlkWithOutState)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))
+	BlkWithOutStateRoot, err := BlkWithOutState.Block.HashTreeRoot()
+	require.NoError(t, err)
+
+	BlkWithStateBadAtt := util.NewBeaconBlock()
+	BlkWithStateBadAtt.Block.Slot = 1
+	wsb, err = wrapper.WrappedSignedBeaconBlock(BlkWithStateBadAtt)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))
+	BlkWithStateBadAttRoot, err := BlkWithStateBadAtt.Block.HashTreeRoot()
+	require.NoError(t, err)
+
+	s, err := util.NewBeaconState()
+	require.NoError(t, err)
+	require.NoError(t, s.SetSlot(100*params.BeaconConfig().SlotsPerEpoch))
+	require.NoError(t, service.cfg.BeaconDB.SaveState(ctx, s, BlkWithStateBadAttRoot))
+
+	BlkWithValidState := util.NewBeaconBlock()
+	BlkWithValidState.Block.Slot = 2
+	wsb, err = wrapper.WrappedSignedBeaconBlock(BlkWithValidState)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))
+
+	BlkWithValidStateRoot, err := BlkWithValidState.Block.HashTreeRoot()
+	require.NoError(t, err)
+	s, err = util.NewBeaconState()
+	require.NoError(t, err)
+	err = s.SetFork(&ethpb.Fork{
+		Epoch:           0,
+		CurrentVersion:  params.BeaconConfig().GenesisForkVersion,
+		PreviousVersion: params.BeaconConfig().GenesisForkVersion,
+	})
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveState(ctx, s, BlkWithValidStateRoot))
+
+	tests := []struct {
+		name      string
+		a         *ethpb.Attestation
+		wantedErr string
+	}{
+		{
+			name:      "attestation's data slot not aligned with target vote",
+			a:         util.HydrateAttestation(&ethpb.Attestation{Data: &ethpb.AttestationData{Slot: params.BeaconConfig().SlotsPerEpoch, Target: &ethpb.Checkpoint{Root: make([]byte, 32)}}}),
+			wantedErr: "slot 32 does not match target epoch 0",
+		},
+		{
+			name:      "no pre state for attestations's target block",
+			a:         util.HydrateAttestation(&ethpb.Attestation{Data: &ethpb.AttestationData{Target: &ethpb.Checkpoint{Root: BlkWithOutStateRoot[:]}}}),
+			wantedErr: "could not get pre state for epoch 0",
+		},
+		{
+			name: "process attestation doesn't match current epoch",
+			a: util.HydrateAttestation(&ethpb.Attestation{Data: &ethpb.AttestationData{Slot: 100 * params.BeaconConfig().SlotsPerEpoch, Target: &ethpb.Checkpoint{Epoch: 100,
+				Root: BlkWithStateBadAttRoot[:]}}}),
+			wantedErr: "target epoch 100 does not match current epoch",
+		},
+		{
+			name:      "process nil attestation",
+			a:         nil,
+			wantedErr: "attestation can't be nil",
+		},
+		{
+			name:      "process nil field (a.Data) in attestation",
+			a:         &ethpb.Attestation{},
+			wantedErr: "attestation's data can't be nil",
+		},
+		{
+			name: "process nil field (a.Target) in attestation",
+			a: &ethpb.Attestation{
+				Data: &ethpb.AttestationData{
+					BeaconBlockRoot: make([]byte, fieldparams.RootLength),
+					Target:          nil,
+					Source:          &ethpb.Checkpoint{Root: make([]byte, fieldparams.RootLength)},
+				},
+				AggregationBits: make([]byte, 1),
+				Signature:       make([]byte, 96),
+			},
+			wantedErr: "attestation's target can't be nil",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			err := service.OnAttestation(ctx, tt.a)
+			if tt.wantedErr != "" {
+				assert.ErrorContains(t, tt.wantedErr, err)
+			} else {
+				assert.NoError(t, err)
+			}
+		})
+	}
+}
+
+func TestStore_OnAttestation_Ok_ProtoArray(t *testing.T) {
+	ctx := context.Background()
+	beaconDB := testDB.SetupDB(t)
+
+	fcs := protoarray.New(0, 0, [32]byte{'a'})
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithStateGen(stategen.New(beaconDB)),
+		WithForkChoiceStore(fcs),
+	}
+	service, err := NewService(ctx, opts...)
 	require.NoError(t, err)
 	genesisState, pks := util.DeterministicGenesisState(t, 64)
-	require.NoError(t, genesisState.SetGenesisTime(uint64(time.Now().Unix())-params.BeaconConfig().SecondsPerSlot))
+	service.SetGenesisTime(time.Unix(time.Now().Unix()-int64(params.BeaconConfig().SecondsPerSlot), 0))
 	require.NoError(t, service.saveGenesisData(ctx, genesisState))
 	att, err := util.GenerateAttestations(genesisState, pks, 1, 0, false)
 	require.NoError(t, err)
@@ -147,28 +268,54 @@ func TestStore_OnAttestation_Ok(t *testing.T) {
 	copied, err = transition.ProcessSlots(ctx, copied, 1)
 	require.NoError(t, err)
 	require.NoError(t, service.cfg.BeaconDB.SaveState(ctx, copied, tRoot))
-	require.NoError(t, service.cfg.ForkChoiceStore.ProcessBlock(ctx, 0, tRoot, tRoot, tRoot, 1, 1))
-	require.NoError(t, service.onAttestation(ctx, att[0]))
+	require.NoError(t, service.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 0, tRoot, tRoot, params.BeaconConfig().ZeroHash, 1, 1))
+	require.NoError(t, service.OnAttestation(ctx, att[0]))
+}
+
+func TestStore_OnAttestation_Ok_DoublyLinkedTree(t *testing.T) {
+	ctx := context.Background()
+	beaconDB := testDB.SetupDB(t)
+
+	fcs := doublylinkedtree.New(0, 0)
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithStateGen(stategen.New(beaconDB)),
+		WithForkChoiceStore(fcs),
+	}
+	service, err := NewService(ctx, opts...)
+	require.NoError(t, err)
+	genesisState, pks := util.DeterministicGenesisState(t, 64)
+	service.SetGenesisTime(time.Unix(time.Now().Unix()-int64(params.BeaconConfig().SecondsPerSlot), 0))
+	require.NoError(t, service.saveGenesisData(ctx, genesisState))
+	att, err := util.GenerateAttestations(genesisState, pks, 1, 0, false)
+	require.NoError(t, err)
+	tRoot := bytesutil.ToBytes32(att[0].Data.Target.Root)
+	copied := genesisState.Copy()
+	copied, err = transition.ProcessSlots(ctx, copied, 1)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveState(ctx, copied, tRoot))
+	require.NoError(t, service.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 0, tRoot, tRoot, params.BeaconConfig().ZeroHash, 1, 1))
+	require.NoError(t, service.OnAttestation(ctx, att[0]))
 }

 func TestStore_SaveCheckpointState(t *testing.T) {
 	ctx := context.Background()
 	beaconDB := testDB.SetupDB(t)

-	cfg := &Config{
-		BeaconDB: beaconDB,
-		StateGen: stategen.New(beaconDB),
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithStateGen(stategen.New(beaconDB)),
 	}
-	service, err := NewService(ctx, cfg)
+	service, err := NewService(ctx, opts...)
 	require.NoError(t, err)

 	s, err := util.NewBeaconState()
 	require.NoError(t, err)
-	err = s.SetFinalizedCheckpoint(&ethpb.Checkpoint{Root: bytesutil.PadTo([]byte{'A'}, 32)})
+	err = s.SetFinalizedCheckpoint(&ethpb.Checkpoint{Root: bytesutil.PadTo([]byte{'A'}, fieldparams.RootLength)})
 	require.NoError(t, err)
 	val := &ethpb.Validator{
 		PublicKey:             bytesutil.PadTo([]byte("foo"), 48),
-		WithdrawalCredentials: bytesutil.PadTo([]byte("bar"), 32),
+		WithdrawalCredentials: bytesutil.PadTo([]byte("bar"), fieldparams.RootLength),
 	}
 	err = s.SetValidators([]*ethpb.Validator{val})
 	require.NoError(t, err)
@@ -177,23 +324,23 @@ func TestStore_SaveCheckpointState(t *testing.T) {
 	r := [32]byte{'g'}
 	require.NoError(t, service.cfg.BeaconDB.SaveState(ctx, s, r))

-	service.justifiedCheckpt = &ethpb.Checkpoint{Root: r[:]}
-	service.bestJustifiedCheckpt = &ethpb.Checkpoint{Root: r[:]}
-	service.finalizedCheckpt = &ethpb.Checkpoint{Root: r[:]}
-	service.prevFinalizedCheckpt = &ethpb.Checkpoint{Root: r[:]}
+	service.store.SetJustifiedCheckpt(&ethpb.Checkpoint{Root: r[:]})
+	service.store.SetBestJustifiedCheckpt(&ethpb.Checkpoint{Root: r[:]})
+	service.store.SetFinalizedCheckpt(&ethpb.Checkpoint{Root: r[:]})
+	service.store.SetPrevFinalizedCheckpt(&ethpb.Checkpoint{Root: r[:]})

 	r = bytesutil.ToBytes32([]byte{'A'})
-	cp1 := &ethpb.Checkpoint{Epoch: 1, Root: bytesutil.PadTo([]byte{'A'}, 32)}
+	cp1 := &ethpb.Checkpoint{Epoch: 1, Root: bytesutil.PadTo([]byte{'A'}, fieldparams.RootLength)}
 	require.NoError(t, service.cfg.BeaconDB.SaveState(ctx, s, bytesutil.ToBytes32([]byte{'A'})))
-	require.NoError(t, service.cfg.BeaconDB.SaveStateSummary(ctx, &ethpb.StateSummary{Root: bytesutil.PadTo([]byte{'A'}, 32)}))
+	require.NoError(t, service.cfg.BeaconDB.SaveStateSummary(ctx, &ethpb.StateSummary{Root: bytesutil.PadTo([]byte{'A'}, fieldparams.RootLength)}))

 	s1, err := service.getAttPreState(ctx, cp1)
 	require.NoError(t, err)
 	assert.Equal(t, 1*params.BeaconConfig().SlotsPerEpoch, s1.Slot(), "Unexpected state slot")

-	cp2 := &ethpb.Checkpoint{Epoch: 2, Root: bytesutil.PadTo([]byte{'B'}, 32)}
+	cp2 := &ethpb.Checkpoint{Epoch: 2, Root: bytesutil.PadTo([]byte{'B'}, fieldparams.RootLength)}
 	require.NoError(t, service.cfg.BeaconDB.SaveState(ctx, s, bytesutil.ToBytes32([]byte{'B'})))
-	require.NoError(t, service.cfg.BeaconDB.SaveStateSummary(ctx, &ethpb.StateSummary{Root: bytesutil.PadTo([]byte{'B'}, 32)}))
+	require.NoError(t, service.cfg.BeaconDB.SaveStateSummary(ctx, &ethpb.StateSummary{Root: bytesutil.PadTo([]byte{'B'}, fieldparams.RootLength)}))
 	s2, err := service.getAttPreState(ctx, cp2)
 	require.NoError(t, err)
 	assert.Equal(t, 2*params.BeaconConfig().SlotsPerEpoch, s2.Slot(), "Unexpected state slot")
@@ -211,13 +358,13 @@ func TestStore_SaveCheckpointState(t *testing.T) {
 	assert.Equal(t, 2*params.BeaconConfig().SlotsPerEpoch, s2.Slot(), "Unexpected state slot")

 	require.NoError(t, s.SetSlot(params.BeaconConfig().SlotsPerEpoch+1))
-	service.justifiedCheckpt = &ethpb.Checkpoint{Root: r[:]}
-	service.bestJustifiedCheckpt = &ethpb.Checkpoint{Root: r[:]}
-	service.finalizedCheckpt = &ethpb.Checkpoint{Root: r[:]}
-	service.prevFinalizedCheckpt = &ethpb.Checkpoint{Root: r[:]}
-	cp3 := &ethpb.Checkpoint{Epoch: 1, Root: bytesutil.PadTo([]byte{'C'}, 32)}
+	service.store.SetJustifiedCheckpt(&ethpb.Checkpoint{Root: r[:]})
+	service.store.SetBestJustifiedCheckpt(&ethpb.Checkpoint{Root: r[:]})
+	service.store.SetFinalizedCheckpt(&ethpb.Checkpoint{Root: r[:]})
+	service.store.SetPrevFinalizedCheckpt(&ethpb.Checkpoint{Root: r[:]})
+	cp3 := &ethpb.Checkpoint{Epoch: 1, Root: bytesutil.PadTo([]byte{'C'}, fieldparams.RootLength)}
 	require.NoError(t, service.cfg.BeaconDB.SaveState(ctx, s, bytesutil.ToBytes32([]byte{'C'})))
-	require.NoError(t, service.cfg.BeaconDB.SaveStateSummary(ctx, &ethpb.StateSummary{Root: bytesutil.PadTo([]byte{'C'}, 32)}))
+	require.NoError(t, service.cfg.BeaconDB.SaveStateSummary(ctx, &ethpb.StateSummary{Root: bytesutil.PadTo([]byte{'C'}, fieldparams.RootLength)}))
 	s3, err := service.getAttPreState(ctx, cp3)
 	require.NoError(t, err)
 	assert.Equal(t, s.Slot(), s3.Slot(), "Unexpected state slot")
@@ -227,16 +374,16 @@ func TestStore_UpdateCheckpointState(t *testing.T) {
 	ctx := context.Background()
 	beaconDB := testDB.SetupDB(t)

-	cfg := &Config{
-		BeaconDB: beaconDB,
-		StateGen: stategen.New(beaconDB),
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithStateGen(stategen.New(beaconDB)),
 	}
-	service, err := NewService(ctx, cfg)
+	service, err := NewService(ctx, opts...)
 	require.NoError(t, err)

 	epoch := types.Epoch(1)
 	baseState, _ := util.DeterministicGenesisState(t, 1)
-	checkpoint := &ethpb.Checkpoint{Epoch: epoch, Root: bytesutil.PadTo([]byte("hi"), 32)}
+	checkpoint := &ethpb.Checkpoint{Epoch: epoch, Root: bytesutil.PadTo([]byte("hi"), fieldparams.RootLength)}
 	require.NoError(t, service.cfg.BeaconDB.SaveState(ctx, baseState, bytesutil.ToBytes32(checkpoint.Root)))
 	returned, err := service.getAttPreState(ctx, checkpoint)
 	require.NoError(t, err)
@@ -247,7 +394,7 @@ func TestStore_UpdateCheckpointState(t *testing.T) {
 	assert.Equal(t, returned.Slot(), cached.Slot(), "State should have been cached")

 	epoch = 2
-	newCheckpoint := &ethpb.Checkpoint{Epoch: epoch, Root: bytesutil.PadTo([]byte("bye"), 32)}
+	newCheckpoint := &ethpb.Checkpoint{Epoch: epoch, Root: bytesutil.PadTo([]byte("bye"), fieldparams.RootLength)}
 	require.NoError(t, service.cfg.BeaconDB.SaveState(ctx, baseState, bytesutil.ToBytes32(newCheckpoint.Root)))
 	returned, err = service.getAttPreState(ctx, newCheckpoint)
 	require.NoError(t, err)
@@ -264,47 +411,30 @@ func TestStore_UpdateCheckpointState(t *testing.T) {

 func TestAttEpoch_MatchPrevEpoch(t *testing.T) {
 	ctx := context.Background()
-	beaconDB := testDB.SetupDB(t)
-
-	cfg := &Config{BeaconDB: beaconDB}
-	service, err := NewService(ctx, cfg)
-	require.NoError(t, err)

 	nowTime := uint64(params.BeaconConfig().SlotsPerEpoch) * params.BeaconConfig().SecondsPerSlot
-	require.NoError(t, service.verifyAttTargetEpoch(ctx, 0, nowTime, &ethpb.Checkpoint{Root: make([]byte, 32)}))
+	require.NoError(t, verifyAttTargetEpoch(ctx, 0, nowTime, &ethpb.Checkpoint{Root: make([]byte, fieldparams.RootLength)}))
 }

 func TestAttEpoch_MatchCurrentEpoch(t *testing.T) {
 	ctx := context.Background()
-	beaconDB := testDB.SetupDB(t)
-
-	cfg := &Config{BeaconDB: beaconDB}
-	service, err := NewService(ctx, cfg)
-	require.NoError(t, err)

 	nowTime := uint64(params.BeaconConfig().SlotsPerEpoch) * params.BeaconConfig().SecondsPerSlot
-	require.NoError(t, service.verifyAttTargetEpoch(ctx, 0, nowTime, &ethpb.Checkpoint{Epoch: 1}))
+	require.NoError(t, verifyAttTargetEpoch(ctx, 0, nowTime, &ethpb.Checkpoint{Epoch: 1}))
 }

 func TestAttEpoch_NotMatch(t *testing.T) {
 	ctx := context.Background()
-	beaconDB := testDB.SetupDB(t)
-
-	cfg := &Config{BeaconDB: beaconDB}
-	service, err := NewService(ctx, cfg)
-	require.NoError(t, err)

 	nowTime := 2 * uint64(params.BeaconConfig().SlotsPerEpoch) * params.BeaconConfig().SecondsPerSlot
-	err = service.verifyAttTargetEpoch(ctx, 0, nowTime, &ethpb.Checkpoint{Root: make([]byte, 32)})
+	err := verifyAttTargetEpoch(ctx, 0, nowTime, &ethpb.Checkpoint{Root: make([]byte, fieldparams.RootLength)})
 	assert.ErrorContains(t, "target epoch 0 does not match current epoch 2 or prev epoch 1", err)
 }

 func TestVerifyBeaconBlock_NoBlock(t *testing.T) {
 	ctx := context.Background()
-	beaconDB := testDB.SetupDB(t)
-
-	cfg := &Config{BeaconDB: beaconDB}
-	service, err := NewService(ctx, cfg)
+	opts := testServiceOptsWithDB(t)
+	service, err := NewService(ctx, opts...)
 	require.NoError(t, err)

 	d := util.HydrateAttestationData(&ethpb.AttestationData{})
@@ -313,15 +443,16 @@ func TestVerifyBeaconBlock_NoBlock(t *testing.T) {

 func TestVerifyBeaconBlock_futureBlock(t *testing.T) {
 	ctx := context.Background()
-	beaconDB := testDB.SetupDB(t)

-	cfg := &Config{BeaconDB: beaconDB}
-	service, err := NewService(ctx, cfg)
+	opts := testServiceOptsWithDB(t)
+	service, err := NewService(ctx, opts...)
 	require.NoError(t, err)

 	b := util.NewBeaconBlock()
 	b.Block.Slot = 2
-	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(b)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(b)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wsb))
 	r, err := b.Block.HashTreeRoot()
 	require.NoError(t, err)
 	d := &ethpb.AttestationData{Slot: 1, BeaconBlockRoot: r[:]}
@@ -331,15 +462,16 @@ func TestVerifyBeaconBlock_futureBlock(t *testing.T) {

 func TestVerifyBeaconBlock_OK(t *testing.T) {
 	ctx := context.Background()
-	beaconDB := testDB.SetupDB(t)

-	cfg := &Config{BeaconDB: beaconDB}
-	service, err := NewService(ctx, cfg)
+	opts := testServiceOptsWithDB(t)
+	service, err := NewService(ctx, opts...)
 	require.NoError(t, err)

 	b := util.NewBeaconBlock()
 	b.Block.Slot = 2
-	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(b)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(b)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wsb))
 	r, err := b.Block.HashTreeRoot()
 	require.NoError(t, err)
 	d := &ethpb.AttestationData{Slot: 2, BeaconBlockRoot: r[:]}
@@ -347,26 +479,69 @@ func TestVerifyBeaconBlock_OK(t *testing.T) {
 	assert.NoError(t, service.verifyBeaconBlock(ctx, d), "Did not receive the wanted error")
 }

-func TestVerifyFinalizedConsistency_InconsistentRoot(t *testing.T) {
+func TestVerifyFinalizedConsistency_InconsistentRoot_ProtoArray(t *testing.T) {
 	ctx := context.Background()
 	beaconDB := testDB.SetupDB(t)

-	cfg := &Config{BeaconDB: beaconDB, ForkChoiceStore: protoarray.New(0, 0, [32]byte{})}
-	service, err := NewService(ctx, cfg)
+	fcs := protoarray.New(0, 0, [32]byte{'a'})
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithStateGen(stategen.New(beaconDB)),
+		WithForkChoiceStore(fcs),
+	}
+	service, err := NewService(ctx, opts...)
 	require.NoError(t, err)

 	b32 := util.NewBeaconBlock()
 	b32.Block.Slot = 32
-	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(b32)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(b32)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wsb))
 	r32, err := b32.Block.HashTreeRoot()
 	require.NoError(t, err)

-	service.finalizedCheckpt = &ethpb.Checkpoint{Epoch: 1}
-
+	service.store.SetFinalizedCheckpt(&ethpb.Checkpoint{Epoch: 1})
 	b33 := util.NewBeaconBlock()
 	b33.Block.Slot = 33
 	b33.Block.ParentRoot = r32[:]
-	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(b33)))
+	wsb, err = wrapper.WrappedSignedBeaconBlock(b33)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wsb))
+	r33, err := b33.Block.HashTreeRoot()
+	require.NoError(t, err)
+
+	err = service.VerifyFinalizedConsistency(context.Background(), r33[:])
+	require.ErrorContains(t, "Root and finalized store are not consistent", err)
+}
+
+func TestVerifyFinalizedConsistency_InconsistentRoot_DoublyLinkedTree(t *testing.T) {
+	ctx := context.Background()
+	beaconDB := testDB.SetupDB(t)
+
+	fcs := doublylinkedtree.New(0, 0)
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithStateGen(stategen.New(beaconDB)),
+		WithForkChoiceStore(fcs),
+	}
+	service, err := NewService(ctx, opts...)
+	require.NoError(t, err)
+
+	b32 := util.NewBeaconBlock()
+	b32.Block.Slot = 32
+	wsb, err := wrapper.WrappedSignedBeaconBlock(b32)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wsb))
+	r32, err := b32.Block.HashTreeRoot()
+	require.NoError(t, err)
+
+	service.store.SetFinalizedCheckpt(&ethpb.Checkpoint{Epoch: 1})
+	b33 := util.NewBeaconBlock()
+	b33.Block.Slot = 33
+	b33.Block.ParentRoot = r32[:]
+	wsb, err = wrapper.WrappedSignedBeaconBlock(b33)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wsb))
 	r33, err := b33.Block.HashTreeRoot()
 	require.NoError(t, err)

@@ -376,24 +551,27 @@ func TestVerifyFinalizedConsistency_InconsistentRoot(t *testing.T) {

 func TestVerifyFinalizedConsistency_OK(t *testing.T) {
 	ctx := context.Background()
-	beaconDB := testDB.SetupDB(t)

-	cfg := &Config{BeaconDB: beaconDB, ForkChoiceStore: protoarray.New(0, 0, [32]byte{})}
-	service, err := NewService(ctx, cfg)
+	opts := testServiceOptsWithDB(t)
+	service, err := NewService(ctx, opts...)
 	require.NoError(t, err)

 	b32 := util.NewBeaconBlock()
 	b32.Block.Slot = 32
-	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(b32)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(b32)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wsb))
 	r32, err := b32.Block.HashTreeRoot()
 	require.NoError(t, err)

-	service.finalizedCheckpt = &ethpb.Checkpoint{Epoch: 1, Root: r32[:]}
+	service.store.SetFinalizedCheckpt(&ethpb.Checkpoint{Root: r32[:], Epoch: 1})

 	b33 := util.NewBeaconBlock()
 	b33.Block.Slot = 33
 	b33.Block.ParentRoot = r32[:]
-	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(b33)))
+	wsb, err = wrapper.WrappedSignedBeaconBlock(b33)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wsb))
 	r33, err := b33.Block.HashTreeRoot()
 	require.NoError(t, err)

@@ -403,10 +581,9 @@ func TestVerifyFinalizedConsistency_OK(t *testing.T) {

 func TestVerifyFinalizedConsistency_IsCanonical(t *testing.T) {
 	ctx := context.Background()
-	beaconDB := testDB.SetupDB(t)

-	cfg := &Config{BeaconDB: beaconDB, ForkChoiceStore: protoarray.New(0, 0, [32]byte{})}
-	service, err := NewService(ctx, cfg)
+	opts := testServiceOptsWithDB(t)
+	service, err := NewService(ctx, opts...)
 	require.NoError(t, err)

 	b32 := util.NewBeaconBlock()
@@ -414,7 +591,7 @@ func TestVerifyFinalizedConsistency_IsCanonical(t *testing.T) {
 	r32, err := b32.Block.HashTreeRoot()
 	require.NoError(t, err)

-	service.finalizedCheckpt = &ethpb.Checkpoint{Epoch: 1, Root: r32[:]}
+	service.store.SetFinalizedCheckpt(&ethpb.Checkpoint{Root: r32[:], Epoch: 1})

 	b33 := util.NewBeaconBlock()
 	b33.Block.Slot = 33
@@ -422,8 +599,8 @@ func TestVerifyFinalizedConsistency_IsCanonical(t *testing.T) {
 	r33, err := b33.Block.HashTreeRoot()
 	require.NoError(t, err)

-	require.NoError(t, service.cfg.ForkChoiceStore.ProcessBlock(ctx, b32.Block.Slot, r32, [32]byte{}, [32]byte{}, 0, 0))
-	require.NoError(t, service.cfg.ForkChoiceStore.ProcessBlock(ctx, b33.Block.Slot, r33, r32, [32]byte{}, 0, 0))
+	require.NoError(t, service.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, b32.Block.Slot, r32, [32]byte{}, params.BeaconConfig().ZeroHash, 0, 0))
+	require.NoError(t, service.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, b33.Block.Slot, r33, r32, params.BeaconConfig().ZeroHash, 0, 0))

 	_, err = service.cfg.ForkChoiceStore.Head(ctx, 0, r32, []uint64{}, 0)
 	require.NoError(t, err)
--- a/beacon-chain/blockchain/process_block.go
+++ b/beacon-chain/blockchain/process_block.go
@@ -6,11 +6,13 @@ import (
 	"time"

 	"github.com/pkg/errors"
+	"github.com/prysmaticlabs/prysm/beacon-chain/core/blocks"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/feed"
 	statefeed "github.com/prysmaticlabs/prysm/beacon-chain/core/feed/state"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
 	coreTime "github.com/prysmaticlabs/prysm/beacon-chain/core/time"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/transition"
+	forkchoicetypes "github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/types"
 	"github.com/prysmaticlabs/prysm/beacon-chain/state"
 	"github.com/prysmaticlabs/prysm/config/features"
 	"github.com/prysmaticlabs/prysm/config/params"
@@ -21,6 +23,7 @@ import (
 	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
 	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/attestation"
 	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/block"
+	"github.com/prysmaticlabs/prysm/runtime/version"
 	"github.com/prysmaticlabs/prysm/time/slots"
 	"go.opencensus.io/trace"
 )
@@ -88,9 +91,8 @@ var initialSyncBlockCacheSize = uint64(2 * params.BeaconConfig().SlotsPerEpoch)
 func (s *Service) onBlock(ctx context.Context, signed block.SignedBeaconBlock, blockRoot [32]byte) error {
 	ctx, span := trace.StartSpan(ctx, "blockChain.onBlock")
 	defer span.End()
-
-	if signed == nil || signed.IsNil() || signed.Block().IsNil() {
-		return errors.New("nil block")
+	if err := helpers.BeaconBlockIsNil(signed); err != nil {
+		return err
 	}
 	b := signed.Block()

@@ -99,14 +101,36 @@ func (s *Service) onBlock(ctx context.Context, signed block.SignedBeaconBlock, b
 		return err
 	}

+	preStateVersion, preStateHeader, err := getStateVersionAndPayload(preState)
+	if err != nil {
+		return err
+	}
 	postState, err := transition.ExecuteStateTransition(ctx, preState, signed)
 	if err != nil {
 		return err
 	}
-
 	if err := s.savePostStateInfo(ctx, blockRoot, signed, postState, false /* reg sync */); err != nil {
 		return err
 	}
+	postStateVersion, postStateHeader, err := getStateVersionAndPayload(postState)
+	if err != nil {
+		return err
+	}
+	if err := s.notifyNewPayload(ctx, preStateVersion, postStateVersion, preStateHeader, postStateHeader, signed, blockRoot); err != nil {
+		return errors.Wrap(err, "could not verify new payload")
+	}
+
+	// We add a proposer score boost to fork choice for the block root if applicable, right after
+	// running a successful state transition for the block.
+	secondsIntoSlot := uint64(time.Since(s.genesisTime).Seconds()) % params.BeaconConfig().SecondsPerSlot
+	if err := s.cfg.ForkChoiceStore.BoostProposerRoot(ctx, &forkchoicetypes.ProposerBoostRootArgs{
+		BlockRoot:       blockRoot,
+		BlockSlot:       signed.Block().Slot(),
+		CurrentSlot:     slots.SinceGenesis(s.genesisTime),
+		SecondsIntoSlot: secondsIntoSlot,
+	}); err != nil {
+		return err
+	}

 	// If slasher is configured, forward the attestations in the block via
 	// an event feed for processing.
@@ -136,25 +160,40 @@ func (s *Service) onBlock(ctx context.Context, signed block.SignedBeaconBlock, b
 	}

 	// Update justified check point.
-	currJustifiedEpoch := s.justifiedCheckpt.Epoch
+	justified := s.store.JustifiedCheckpt()
+	if justified == nil {
+		return errNilJustifiedInStore
+	}
+	currJustifiedEpoch := justified.Epoch
 	if postState.CurrentJustifiedCheckpoint().Epoch > currJustifiedEpoch {
 		if err := s.updateJustified(ctx, postState); err != nil {
 			return err
 		}
 	}

-	newFinalized := postState.FinalizedCheckpointEpoch() > s.finalizedCheckpt.Epoch
+	finalized := s.store.FinalizedCheckpt()
+	if finalized == nil {
+		return errNilFinalizedInStore
+	}
+	newFinalized := postState.FinalizedCheckpointEpoch() > finalized.Epoch
 	if newFinalized {
-		if err := s.finalizedImpliesNewJustified(ctx, postState); err != nil {
-			return errors.Wrap(err, "could not save new justified")
-		}
-		s.prevFinalizedCheckpt = s.finalizedCheckpt
-		s.finalizedCheckpt = postState.FinalizedCheckpoint()
+		s.store.SetPrevFinalizedCheckpt(finalized)
+		s.store.SetFinalizedCheckpt(postState.FinalizedCheckpoint())
+		s.store.SetPrevJustifiedCheckpt(justified)
+		s.store.SetJustifiedCheckpt(postState.CurrentJustifiedCheckpoint())
 	}

-	if err := s.updateHead(ctx, s.getJustifiedBalances()); err != nil {
+	balances, err := s.justifiedBalances.get(ctx, bytesutil.ToBytes32(justified.Root))
+	if err != nil {
+		msg := fmt.Sprintf("could not read balances for state w/ justified checkpoint %#x", justified.Root)
+		return errors.Wrap(err, msg)
+	}
+	if err := s.updateHead(ctx, balances); err != nil {
 		log.WithError(err).Warn("Could not update head")
 	}
+	if _, err := s.notifyForkchoiceUpdate(ctx, s.headBlock().Block(), s.headRoot(), bytesutil.ToBytes32(finalized.Root)); err != nil {
+		return err
+	}

 	if err := s.pruneCanonicalAttsFromPool(ctx, blockRoot, signed); err != nil {
 		return err
@@ -172,18 +211,16 @@ func (s *Service) onBlock(ctx context.Context, signed block.SignedBeaconBlock, b
 	})

 	// Updating next slot state cache can happen in the background. It shouldn't block rest of the process.
-	if features.Get().EnableNextSlotStateCache {
-		go func() {
-			// Use a custom deadline here, since this method runs asynchronously.
-			// We ignore the parent method's context and instead create a new one
-			// with a custom deadline, therefore using the background context instead.
-			slotCtx, cancel := context.WithTimeout(context.Background(), slotDeadline)
-			defer cancel()
-			if err := transition.UpdateNextSlotCache(slotCtx, blockRoot[:], postState); err != nil {
-				log.WithError(err).Debug("could not update next slot state cache")
-			}
-		}()
-	}
+	go func() {
+		// Use a custom deadline here, since this method runs asynchronously.
+		// We ignore the parent method's context and instead create a new one
+		// with a custom deadline, therefore using the background context instead.
+		slotCtx, cancel := context.WithTimeout(context.Background(), slotDeadline)
+		defer cancel()
+		if err := transition.UpdateNextSlotCache(slotCtx, blockRoot[:], postState); err != nil {
+			log.WithError(err).Debug("could not update next slot state cache")
+		}
+	}()

 	// Save justified check point to db.
 	if postState.CurrentJustifiedCheckpoint().Epoch > currJustifiedEpoch {
@@ -201,14 +238,19 @@ func (s *Service) onBlock(ctx context.Context, signed block.SignedBeaconBlock, b
 		if err := s.cfg.ForkChoiceStore.Prune(ctx, fRoot); err != nil {
 			return errors.Wrap(err, "could not prune proto array fork choice nodes")
 		}
+		isOptimistic, err := s.cfg.ForkChoiceStore.IsOptimistic(ctx, fRoot)
+		if err != nil {
+			return errors.Wrap(err, "could not check if node is optimistically synced")
+		}
 		go func() {
 			// Send an event regarding the new finalized checkpoint over a common event feed.
 			s.cfg.StateNotifier.StateFeed().Send(&feed.Event{
 				Type: statefeed.FinalizedCheckpoint,
 				Data: &ethpbv1.EventFinalizedCheckpoint{
-					Epoch: postState.FinalizedCheckpoint().Epoch,
-					Block: postState.FinalizedCheckpoint().Root,
-					State: signed.Block().StateRoot(),
+					Epoch:               postState.FinalizedCheckpoint().Epoch,
+					Block:               postState.FinalizedCheckpoint().Root,
+					State:               signed.Block().StateRoot(),
+					ExecutionOptimistic: isOptimistic,
 				},
 			})

@@ -229,6 +271,24 @@ func (s *Service) onBlock(ctx context.Context, signed block.SignedBeaconBlock, b
 	return s.handleEpochBoundary(ctx, postState)
 }

+func getStateVersionAndPayload(st state.BeaconState) (int, *ethpb.ExecutionPayloadHeader, error) {
+	if st == nil {
+		return 0, nil, errors.New("nil state")
+	}
+	var preStateHeader *ethpb.ExecutionPayloadHeader
+	var err error
+	preStateVersion := st.Version()
+	switch preStateVersion {
+	case version.Phase0, version.Altair:
+	default:
+		preStateHeader, err = st.LatestExecutionPayloadHeader()
+		if err != nil {
+			return 0, nil, err
+		}
+	}
+	return preStateVersion, preStateHeader, nil
+}
+
 func (s *Service) onBlockBatch(ctx context.Context, blks []block.SignedBeaconBlock,
 	blockRoots [][32]byte) ([]*ethpb.Checkpoint, []*ethpb.Checkpoint, error) {
 	ctx, span := trace.StartSpan(ctx, "blockChain.onBlockBatch")
@@ -237,8 +297,13 @@ func (s *Service) onBlockBatch(ctx context.Context, blks []block.SignedBeaconBlo
 	if len(blks) == 0 || len(blockRoots) == 0 {
 		return nil, nil, errors.New("no blocks provided")
 	}
-	if blks[0] == nil || blks[0].IsNil() || blks[0].Block().IsNil() {
-		return nil, nil, errors.New("nil block")
+
+	if len(blks) != len(blockRoots) {
+		return nil, nil, errWrongBlockCount
+	}
+
+	if err := helpers.BeaconBlockIsNil(blks[0]); err != nil {
+		return nil, nil, err
 	}
 	b := blks[0].Block()

@@ -256,14 +321,29 @@ func (s *Service) onBlockBatch(ctx context.Context, blks []block.SignedBeaconBlo

 	jCheckpoints := make([]*ethpb.Checkpoint, len(blks))
 	fCheckpoints := make([]*ethpb.Checkpoint, len(blks))
-	sigSet := &bls.SignatureSet{
+	sigSet := &bls.SignatureBatch{
 		Signatures: [][]byte{},
 		PublicKeys: []bls.PublicKey{},
 		Messages:   [][32]byte{},
 	}
-	var set *bls.SignatureSet
+	type versionAndHeader struct {
+		version int
+		header  *ethpb.ExecutionPayloadHeader
+	}
+	preVersionAndHeaders := make([]*versionAndHeader, len(blks))
+	postVersionAndHeaders := make([]*versionAndHeader, len(blks))
+	var set *bls.SignatureBatch
 	boundaries := make(map[[32]byte]state.BeaconState)
 	for i, b := range blks {
+		v, h, err := getStateVersionAndPayload(preState)
+		if err != nil {
+			return nil, nil, err
+		}
+		preVersionAndHeaders[i] = &versionAndHeader{
+			version: v,
+			header:  h,
+		}
+
 		set, preState, err = transition.ExecuteStateTransitionNoVerifyAnySig(ctx, preState, b)
 		if err != nil {
 			return nil, nil, err
@@ -271,12 +351,18 @@ func (s *Service) onBlockBatch(ctx context.Context, blks []block.SignedBeaconBlo
 		// Save potential boundary states.
 		if slots.IsEpochStart(preState.Slot()) {
 			boundaries[blockRoots[i]] = preState.Copy()
-			if err := s.handleEpochBoundary(ctx, preState); err != nil {
-				return nil, nil, errors.Wrap(err, "could not handle epoch boundary state")
-			}
 		}
 		jCheckpoints[i] = preState.CurrentJustifiedCheckpoint()
 		fCheckpoints[i] = preState.FinalizedCheckpoint()
+
+		v, h, err = getStateVersionAndPayload(preState)
+		if err != nil {
+			return nil, nil, err
+		}
+		postVersionAndHeaders[i] = &versionAndHeader{
+			version: v,
+			header:  h,
+		}
 		sigSet.Join(set)
 	}
 	verify, err := sigSet.Verify()
@@ -286,6 +372,26 @@ func (s *Service) onBlockBatch(ctx context.Context, blks []block.SignedBeaconBlo
 	if !verify {
 		return nil, nil, errors.New("batch block signature verification failed")
 	}
+
+	// blocks have been verified, add them to forkchoice and call the engine
+	for i, b := range blks {
+		s.saveInitSyncBlock(blockRoots[i], b)
+		if err := s.insertBlockToForkChoiceStore(ctx, b.Block(), blockRoots[i], fCheckpoints[i], jCheckpoints[i]); err != nil {
+			return nil, nil, err
+		}
+		if err := s.notifyNewPayload(ctx,
+			preVersionAndHeaders[i].version,
+			postVersionAndHeaders[i].version,
+			preVersionAndHeaders[i].header,
+			postVersionAndHeaders[i].header, b, blockRoots[i]); err != nil {
+			return nil, nil, err
+		}
+
+		if _, err := s.notifyForkchoiceUpdate(ctx, b.Block(), blockRoots[i], bytesutil.ToBytes32(fCheckpoints[i].Root)); err != nil {
+			return nil, nil, err
+		}
+	}
+
 	for r, st := range boundaries {
 		if err := s.cfg.StateGen.SaveState(ctx, r, st); err != nil {
 			return nil, nil, err
@@ -307,12 +413,7 @@ func (s *Service) onBlockBatch(ctx context.Context, blks []block.SignedBeaconBlo
 // their state summaries and split them off to relative hot/cold storage.
 func (s *Service) handleBlockAfterBatchVerify(ctx context.Context, signed block.SignedBeaconBlock,
 	blockRoot [32]byte, fCheckpoint, jCheckpoint *ethpb.Checkpoint) error {
-	b := signed.Block()

-	s.saveInitSyncBlock(blockRoot, signed)
-	if err := s.insertBlockToForkChoiceStore(ctx, b, blockRoot, fCheckpoint, jCheckpoint); err != nil {
-		return err
-	}
 	if err := s.cfg.BeaconDB.SaveStateSummary(ctx, &ethpb.StateSummary{
 		Slot: signed.Block().Slot(),
 		Root: blockRoot[:],
@@ -328,19 +429,27 @@ func (s *Service) handleBlockAfterBatchVerify(ctx context.Context, signed block.
 		s.clearInitSyncBlocks()
 	}

-	if jCheckpoint.Epoch > s.justifiedCheckpt.Epoch {
+	justified := s.store.JustifiedCheckpt()
+	if justified == nil {
+		return errNilJustifiedInStore
+	}
+	if jCheckpoint.Epoch > justified.Epoch {
 		if err := s.updateJustifiedInitSync(ctx, jCheckpoint); err != nil {
 			return err
 		}
 	}

+	finalized := s.store.FinalizedCheckpt()
+	if finalized == nil {
+		return errNilFinalizedInStore
+	}
 	// Update finalized check point. Prune the block cache and helper caches on every new finalized epoch.
-	if fCheckpoint.Epoch > s.finalizedCheckpt.Epoch {
+	if fCheckpoint.Epoch > finalized.Epoch {
 		if err := s.updateFinalized(ctx, fCheckpoint); err != nil {
 			return err
 		}
-		s.prevFinalizedCheckpt = s.finalizedCheckpt
-		s.finalizedCheckpt = fCheckpoint
+		s.store.SetPrevFinalizedCheckpt(finalized)
+		s.store.SetFinalizedCheckpt(fCheckpoint)
 	}
 	return nil
 }
@@ -419,13 +528,27 @@ func (s *Service) insertBlockToForkChoiceStore(ctx context.Context, blk block.Be
 		return err
 	}
 	// Feed in block to fork choice store.
-	if err := s.cfg.ForkChoiceStore.ProcessBlock(ctx,
-		blk.Slot(), root, bytesutil.ToBytes32(blk.ParentRoot()), bytesutil.ToBytes32(blk.Body().Graffiti()),
-		jCheckpoint.Epoch,
-		fCheckpoint.Epoch); err != nil {
-		return errors.Wrap(err, "could not process block for proto array fork choice")
+
+	payloadHash, err := getBlockPayloadHash(blk)
+	if err != nil {
+		return err
 	}
-	return nil
+	return s.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx,
+		blk.Slot(), root, bytesutil.ToBytes32(blk.ParentRoot()), payloadHash,
+		jCheckpoint.Epoch,
+		fCheckpoint.Epoch)
+}
+
+func getBlockPayloadHash(blk block.BeaconBlock) ([32]byte, error) {
+	payloadHash := [32]byte{}
+	if blocks.IsPreBellatrixVersion(blk.Version()) {
+		return payloadHash, nil
+	}
+	payload, err := blk.Body().ExecutionPayload()
+	if err != nil {
+		return payloadHash, err
+	}
+	return bytesutil.ToBytes32(payload.BlockHash), nil
 }

 // This saves post state info to DB or cache. This also saves post state info to fork choice store.
--- a/beacon-chain/blockchain/process_block_helpers.go
+++ b/beacon-chain/blockchain/process_block_helpers.go
@@ -13,7 +13,6 @@ import (
 	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
 	"github.com/prysmaticlabs/prysm/monitoring/tracing"
 	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
-	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/attestation"
 	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/block"
 	"github.com/prysmaticlabs/prysm/time/slots"
 	"go.opencensus.io/trace"
@@ -45,7 +44,7 @@ func (s *Service) getBlockPreState(ctx context.Context, b block.BeaconBlock) (st
 	}

 	// Verify block slot time is not from the future.
-	if err := slots.VerifyTime(preState.GenesisTime(), b.Slot(), params.BeaconNetworkConfig().MaximumGossipClockDisparity); err != nil {
+	if err := slots.VerifyTime(uint64(s.genesisTime.Unix()), b.Slot(), params.BeaconNetworkConfig().MaximumGossipClockDisparity); err != nil {
 		return nil, err
 	}

@@ -92,7 +91,11 @@ func (s *Service) verifyBlkPreState(ctx context.Context, b block.BeaconBlock) er
 func (s *Service) VerifyBlkDescendant(ctx context.Context, root [32]byte) error {
 	ctx, span := trace.StartSpan(ctx, "blockChain.VerifyBlkDescendant")
 	defer span.End()
-	fRoot := s.ensureRootNotZeros(bytesutil.ToBytes32(s.finalizedCheckpt.Root))
+	finalized := s.store.FinalizedCheckpt()
+	if finalized == nil {
+		return errNilFinalizedInStore
+	}
+	fRoot := s.ensureRootNotZeros(bytesutil.ToBytes32(finalized.Root))
 	finalizedBlkSigned, err := s.cfg.BeaconDB.Block(ctx, fRoot)
 	if err != nil {
 		return err
@@ -110,7 +113,7 @@ func (s *Service) VerifyBlkDescendant(ctx context.Context, root [32]byte) error
 	}

 	if !bytes.Equal(bFinalizedRoot, fRoot[:]) {
-		err := fmt.Errorf("block %#x is not a descendent of the current finalized block slot %d, %#x != %#x",
+		err := fmt.Errorf("block %#x is not a descendant of the current finalized block slot %d, %#x != %#x",
 			bytesutil.Trunc(root[:]), finalizedBlk.Slot(), bytesutil.Trunc(bFinalizedRoot),
 			bytesutil.Trunc(fRoot[:]))
 		tracing.AnnotateError(span, err)
@@ -122,7 +125,11 @@ func (s *Service) VerifyBlkDescendant(ctx context.Context, root [32]byte) error
 // verifyBlkFinalizedSlot validates input block is not less than or equal
 // to current finalized slot.
 func (s *Service) verifyBlkFinalizedSlot(b block.BeaconBlock) error {
-	finalizedSlot, err := slots.EpochStart(s.finalizedCheckpt.Epoch)
+	finalized := s.store.FinalizedCheckpt()
+	if finalized == nil {
+		return errNilFinalizedInStore
+	}
+	finalizedSlot, err := slots.EpochStart(finalized.Epoch)
 	if err != nil {
 		return err
 	}
@@ -135,7 +142,24 @@ func (s *Service) verifyBlkFinalizedSlot(b block.BeaconBlock) error {
 // shouldUpdateCurrentJustified prevents bouncing attack, by only update conflicting justified
 // checkpoints in the fork choice if in the early slots of the epoch.
 // Otherwise, delay incorporation of new justified checkpoint until next epoch boundary.
-// See https://ethresear.ch/t/prevention-of-bouncing-attack-on-ffg/6114 for more detailed analysis and discussion.
+//
+// Spec code:
+// def should_update_justified_checkpoint(store: Store, new_justified_checkpoint: Checkpoint) -> bool:
+//    """
+//    To address the bouncing attack, only update conflicting justified
+//    checkpoints in the fork choice if in the early slots of the epoch.
+//    Otherwise, delay incorporation of new justified checkpoint until next epoch boundary.
+//
+//    See https://ethresear.ch/t/prevention-of-bouncing-attack-on-ffg/6114 for more detailed analysis and discussion.
+//    """
+//    if compute_slots_since_epoch_start(get_current_slot(store)) < SAFE_SLOTS_TO_UPDATE_JUSTIFIED:
+//        return True
+//
+//    justified_slot = compute_start_slot_at_epoch(store.justified_checkpoint.epoch)
+//    if not get_ancestor(store, new_justified_checkpoint.root, justified_slot) == store.justified_checkpoint.root:
+//        return False
+//
+//    return True
 func (s *Service) shouldUpdateCurrentJustified(ctx context.Context, newJustifiedCheckpt *ethpb.Checkpoint) (bool, error) {
 	ctx, span := trace.StartSpan(ctx, "blockChain.shouldUpdateCurrentJustified")
 	defer span.End()
@@ -143,51 +167,20 @@ func (s *Service) shouldUpdateCurrentJustified(ctx context.Context, newJustified
 	if slots.SinceEpochStarts(s.CurrentSlot()) < params.BeaconConfig().SafeSlotsToUpdateJustified {
 		return true, nil
 	}
-	var newJustifiedBlockSigned block.SignedBeaconBlock
+	justified := s.store.JustifiedCheckpt()
+	jSlot, err := slots.EpochStart(justified.Epoch)
+	if err != nil {
+		return false, err
+	}
 	justifiedRoot := s.ensureRootNotZeros(bytesutil.ToBytes32(newJustifiedCheckpt.Root))
-	var err error
-	if s.hasInitSyncBlock(justifiedRoot) {
-		newJustifiedBlockSigned = s.getInitSyncBlock(justifiedRoot)
-	} else {
-		newJustifiedBlockSigned, err = s.cfg.BeaconDB.Block(ctx, justifiedRoot)
-		if err != nil {
-			return false, err
-		}
-	}
-	if newJustifiedBlockSigned == nil || newJustifiedBlockSigned.IsNil() || newJustifiedBlockSigned.Block().IsNil() {
-		return false, errors.New("nil new justified block")
-	}
-
-	newJustifiedBlock := newJustifiedBlockSigned.Block()
-	jSlot, err := slots.EpochStart(s.justifiedCheckpt.Epoch)
+	b, err := s.ancestor(ctx, justifiedRoot[:], jSlot)
 	if err != nil {
 		return false, err
 	}
-	if newJustifiedBlock.Slot() <= jSlot {
+	if !bytes.Equal(b, justified.Root) {
 		return false, nil
 	}
-	var justifiedBlockSigned block.SignedBeaconBlock
-	cachedJustifiedRoot := s.ensureRootNotZeros(bytesutil.ToBytes32(s.justifiedCheckpt.Root))
-	if s.hasInitSyncBlock(cachedJustifiedRoot) {
-		justifiedBlockSigned = s.getInitSyncBlock(cachedJustifiedRoot)
-	} else {
-		justifiedBlockSigned, err = s.cfg.BeaconDB.Block(ctx, cachedJustifiedRoot)
-		if err != nil {
-			return false, err
-		}
-	}

-	if justifiedBlockSigned == nil || justifiedBlockSigned.IsNil() || justifiedBlockSigned.Block().IsNil() {
-		return false, errors.New("nil justified block")
-	}
-	justifiedBlock := justifiedBlockSigned.Block()
-	b, err := s.ancestor(ctx, justifiedRoot[:], justifiedBlock.Slot())
-	if err != nil {
-		return false, err
-	}
-	if !bytes.Equal(b, s.justifiedCheckpt.Root) {
-		return false, nil
-	}
 	return true, nil
 }

@@ -196,8 +189,12 @@ func (s *Service) updateJustified(ctx context.Context, state state.ReadOnlyBeaco
 	defer span.End()

 	cpt := state.CurrentJustifiedCheckpoint()
-	if cpt.Epoch > s.bestJustifiedCheckpt.Epoch {
-		s.bestJustifiedCheckpt = cpt
+	bestJustified := s.store.BestJustifiedCheckpt()
+	if bestJustified == nil {
+		return errNilBestJustifiedInStore
+	}
+	if cpt.Epoch > bestJustified.Epoch {
+		s.store.SetBestJustifiedCheckpt(cpt)
 	}
 	canUpdate, err := s.shouldUpdateCurrentJustified(ctx, cpt)
 	if err != nil {
@@ -205,11 +202,12 @@ func (s *Service) updateJustified(ctx context.Context, state state.ReadOnlyBeaco
 	}

 	if canUpdate {
-		s.prevJustifiedCheckpt = s.justifiedCheckpt
-		s.justifiedCheckpt = cpt
-		if err := s.cacheJustifiedStateBalances(ctx, bytesutil.ToBytes32(s.justifiedCheckpt.Root)); err != nil {
-			return err
+		justified := s.store.JustifiedCheckpt()
+		if justified == nil {
+			return errNilJustifiedInStore
 		}
+		s.store.SetPrevJustifiedCheckpt(justified)
+		s.store.SetJustifiedCheckpt(cpt)
 	}

 	return nil
@@ -219,13 +217,18 @@ func (s *Service) updateJustified(ctx context.Context, state state.ReadOnlyBeaco
 // caches justified checkpoint balances for fork choice and save justified checkpoint in DB.
 // This method does not have defense against fork choice bouncing attack, which is why it's only recommend to be used during initial syncing.
 func (s *Service) updateJustifiedInitSync(ctx context.Context, cp *ethpb.Checkpoint) error {
-	s.prevJustifiedCheckpt = s.justifiedCheckpt
-	s.justifiedCheckpt = cp
-	if err := s.cacheJustifiedStateBalances(ctx, bytesutil.ToBytes32(s.justifiedCheckpt.Root)); err != nil {
+	justified := s.store.JustifiedCheckpt()
+	if justified == nil {
+		return errNilJustifiedInStore
+	}
+	s.store.SetPrevJustifiedCheckpt(justified)
+
+	if err := s.cfg.BeaconDB.SaveJustifiedCheckpoint(ctx, cp); err != nil {
 		return err
 	}
+	s.store.SetJustifiedCheckpt(cp)

-	return s.cfg.BeaconDB.SaveJustifiedCheckpoint(ctx, cp)
+	return nil
 }

 func (s *Service) updateFinalized(ctx context.Context, cp *ethpb.Checkpoint) error {
@@ -244,10 +247,19 @@ func (s *Service) updateFinalized(ctx context.Context, cp *ethpb.Checkpoint) err
 	}

 	fRoot := bytesutil.ToBytes32(cp.Root)
+	optimistic, err := s.cfg.ForkChoiceStore.IsOptimistic(ctx, fRoot)
+	if err != nil {
+		return err
+	}
+	if !optimistic {
+		err = s.cfg.BeaconDB.SaveLastValidatedCheckpoint(ctx, cp)
+		if err != nil {
+			return err
+		}
+	}
 	if err := s.cfg.StateGen.MigrateToCold(ctx, fRoot); err != nil {
 		return errors.Wrap(err, "could not migrate to cold")
 	}
-
 	return nil
 }

@@ -324,49 +336,6 @@ func (s *Service) ancestorByDB(ctx context.Context, r [32]byte, slot types.Slot)
 	return s.ancestorByDB(ctx, bytesutil.ToBytes32(b.ParentRoot()), slot)
 }

-// This updates justified check point in store, if the new justified is later than stored justified or
-// the store's justified is not in chain with finalized check point.
-//
-// Spec definition:
-//   # Potentially update justified if different from store
-//        if store.justified_checkpoint != state.current_justified_checkpoint:
-//            # Update justified if new justified is later than store justified
-//            if state.current_justified_checkpoint.epoch > store.justified_checkpoint.epoch:
-//                store.justified_checkpoint = state.current_justified_checkpoint
-//                return
-//            # Update justified if store justified is not in chain with finalized checkpoint
-//            finalized_slot = compute_start_slot_at_epoch(store.finalized_checkpoint.epoch)
-//            ancestor_at_finalized_slot = get_ancestor(store, store.justified_checkpoint.root, finalized_slot)
-//            if ancestor_at_finalized_slot != store.finalized_checkpoint.root:
-//                store.justified_checkpoint = state.current_justified_checkpoint
-func (s *Service) finalizedImpliesNewJustified(ctx context.Context, state state.BeaconState) error {
-	// Update justified if it's different than the one cached in the store.
-	if !attestation.CheckPointIsEqual(s.justifiedCheckpt, state.CurrentJustifiedCheckpoint()) {
-		if state.CurrentJustifiedCheckpoint().Epoch > s.justifiedCheckpt.Epoch {
-			s.justifiedCheckpt = state.CurrentJustifiedCheckpoint()
-			return s.cacheJustifiedStateBalances(ctx, bytesutil.ToBytes32(s.justifiedCheckpt.Root))
-		}
-
-		// Update justified if store justified is not in chain with finalized check point.
-		finalizedSlot, err := slots.EpochStart(s.finalizedCheckpt.Epoch)
-		if err != nil {
-			return err
-		}
-		justifiedRoot := s.ensureRootNotZeros(bytesutil.ToBytes32(s.justifiedCheckpt.Root))
-		anc, err := s.ancestor(ctx, justifiedRoot[:], finalizedSlot)
-		if err != nil {
-			return err
-		}
-		if !bytes.Equal(anc, s.finalizedCheckpt.Root) {
-			s.justifiedCheckpt = state.CurrentJustifiedCheckpoint()
-			if err := s.cacheJustifiedStateBalances(ctx, bytesutil.ToBytes32(s.justifiedCheckpt.Root)); err != nil {
-				return err
-			}
-		}
-	}
-	return nil
-}
-
 // This retrieves missing blocks from DB (ie. the blocks that couldn't be received over sync) and inserts them to fork choice store.
 // This is useful for block tree visualizer and additional vote accounting.
 func (s *Service) fillInForkChoiceMissingBlocks(ctx context.Context, blk block.BeaconBlock,
@@ -377,7 +346,11 @@ func (s *Service) fillInForkChoiceMissingBlocks(ctx context.Context, blk block.B
 	parentRoot := bytesutil.ToBytes32(blk.ParentRoot())
 	slot := blk.Slot()
 	// Fork choice only matters from last finalized slot.
-	fSlot, err := slots.EpochStart(s.finalizedCheckpt.Epoch)
+	finalized := s.store.FinalizedCheckpt()
+	if finalized == nil {
+		return errNilFinalizedInStore
+	}
+	fSlot, err := slots.EpochStart(finalized.Epoch)
 	if err != nil {
 		return err
 	}
@@ -402,14 +375,17 @@ func (s *Service) fillInForkChoiceMissingBlocks(ctx context.Context, blk block.B
 	for i := len(pendingNodes) - 1; i >= 0; i-- {
 		b := pendingNodes[i]
 		r := pendingRoots[i]
-		if err := s.cfg.ForkChoiceStore.ProcessBlock(ctx,
-			b.Slot(), r, bytesutil.ToBytes32(b.ParentRoot()), bytesutil.ToBytes32(b.Body().Graffiti()),
+		payloadHash, err := getBlockPayloadHash(blk)
+		if err != nil {
+			return err
+		}
+		if err := s.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx,
+			b.Slot(), r, bytesutil.ToBytes32(b.ParentRoot()), payloadHash,
 			jCheckpoint.Epoch,
 			fCheckpoint.Epoch); err != nil {
 			return errors.Wrap(err, "could not process block for proto array fork choice")
 		}
 	}
-
 	return nil
 }

@@ -456,7 +432,7 @@ func (s *Service) deletePoolAtts(atts []*ethpb.Attestation) error {
 // fork choice justification routine.
 func (s *Service) ensureRootNotZeros(root [32]byte) [32]byte {
 	if root == params.BeaconConfig().ZeroHash {
-		return s.genesisRoot
+		return s.originBlockRoot
 	}
 	return root
 }
--- a/beacon-chain/blockchain/process_block_test.go
+++ b/beacon-chain/blockchain/process_block_test.go
--- a/beacon-chain/blockchain/receive_attestation.go
+++ b/beacon-chain/blockchain/receive_attestation.go
@@ -7,6 +7,7 @@ import (
 	"time"

 	"github.com/pkg/errors"
+	"github.com/prysmaticlabs/prysm/async/event"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/feed"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
 	"github.com/prysmaticlabs/prysm/beacon-chain/state"
@@ -41,7 +42,7 @@ func (s *Service) ReceiveAttestationNoPubsub(ctx context.Context, att *ethpb.Att
 	ctx, span := trace.StartSpan(ctx, "beacon-chain.blockchain.ReceiveAttestationNoPubsub")
 	defer span.End()

-	if err := s.onAttestation(ctx, att); err != nil {
+	if err := s.OnAttestation(ctx, att); err != nil {
 		return errors.Wrap(err, "could not process attestation")
 	}

@@ -87,6 +88,9 @@ func (s *Service) VerifyFinalizedConsistency(ctx context.Context, root []byte) e
 	}

 	f := s.FinalizedCheckpt()
+	if f == nil {
+		return errNilFinalizedInStore
+	}
 	ss, err := slots.EpochStart(f.Epoch)
 	if err != nil {
 		return err
@@ -103,38 +107,87 @@ func (s *Service) VerifyFinalizedConsistency(ctx context.Context, root []byte) e
 }

 // This routine processes fork choice attestations from the pool to account for validator votes and fork choice.
-func (s *Service) processAttestationsRoutine(subscribedToStateEvents chan<- struct{}) {
+func (s *Service) spawnProcessAttestationsRoutine(stateFeed *event.Feed) {
 	// Wait for state to be initialized.
 	stateChannel := make(chan *feed.Event, 1)
-	stateSub := s.cfg.StateNotifier.StateFeed().Subscribe(stateChannel)
-	subscribedToStateEvents <- struct{}{}
-	<-stateChannel
-	stateSub.Unsubscribe()
-
-	if s.genesisTime.IsZero() {
-		log.Warn("ProcessAttestations routine waiting for genesis time")
-		for s.genesisTime.IsZero() {
-			time.Sleep(1 * time.Second)
-		}
-		log.Warn("Genesis time received, now available to process attestations")
-	}
-
-	st := slots.NewSlotTicker(s.genesisTime, params.BeaconConfig().SecondsPerSlot)
-	for {
+	stateSub := stateFeed.Subscribe(stateChannel)
+	go func() {
 		select {
 		case <-s.ctx.Done():
+			stateSub.Unsubscribe()
 			return
-		case <-st.C():
-			// Continue when there's no fork choice attestation, there's nothing to process and update head.
-			// This covers the condition when the node is still initial syncing to the head of the chain.
-			if s.cfg.AttPool.ForkchoiceAttestationCount() == 0 {
-				continue
+		case <-stateChannel:
+			stateSub.Unsubscribe()
+			break
+		}
+
+		if s.genesisTime.IsZero() {
+			log.Warn("ProcessAttestations routine waiting for genesis time")
+			for s.genesisTime.IsZero() {
+				if err := s.ctx.Err(); err != nil {
+					log.WithError(err).Error("Giving up waiting for genesis time")
+					return
+				}
+				time.Sleep(1 * time.Second)
 			}
-			s.processAttestations(s.ctx)
-			if err := s.updateHead(s.ctx, s.getJustifiedBalances()); err != nil {
-				log.Warnf("Resolving fork due to new attestation: %v", err)
+			log.Warn("Genesis time received, now available to process attestations")
+		}
+
+		st := slots.NewSlotTicker(s.genesisTime, params.BeaconConfig().SecondsPerSlot)
+		for {
+			select {
+			case <-s.ctx.Done():
+				return
+			case <-st.C():
+				if err := s.NewSlot(s.ctx, s.CurrentSlot()); err != nil {
+					log.WithError(err).Error("Could not process new slot")
+					return
+				}
+
+				// Continue when there's no fork choice attestation, there's nothing to process and update head.
+				// This covers the condition when the node is still initial syncing to the head of the chain.
+				if s.cfg.AttPool.ForkchoiceAttestationCount() == 0 {
+					continue
+				}
+				s.processAttestations(s.ctx)
+
+				justified := s.store.JustifiedCheckpt()
+				if justified == nil {
+					log.WithError(errNilJustifiedInStore).Error("Could not get justified checkpoint")
+					continue
+				}
+				balances, err := s.justifiedBalances.get(s.ctx, bytesutil.ToBytes32(justified.Root))
+				if err != nil {
+					log.WithError(err).Errorf("Unable to get justified balances for root %v", justified.Root)
+					continue
+				}
+				prevHead := s.headRoot()
+				if err := s.updateHead(s.ctx, balances); err != nil {
+					log.WithError(err).Warn("Resolving fork due to new attestation")
+				}
+				s.notifyEngineIfChangedHead(prevHead)
 			}
 		}
+	}()
+}
+
+// This calls notify Forkchoice Update in the event that the head has changed
+func (s *Service) notifyEngineIfChangedHead(prevHead [32]byte) {
+	if s.headRoot() == prevHead {
+		return
+	}
+	finalized := s.store.FinalizedCheckpt()
+	if finalized == nil {
+		log.WithError(errNilFinalizedInStore).Error("could not get finalized checkpoint")
+		return
+	}
+	_, err := s.notifyForkchoiceUpdate(s.ctx,
+		s.headBlock().Block(),
+		s.headRoot(),
+		bytesutil.ToBytes32(finalized.Root),
+	)
+	if err != nil {
+		log.WithError(err).Error("could not notify forkchoice update")
 	}
 }

--- a/beacon-chain/blockchain/receive_attestation_test.go
+++ b/beacon-chain/blockchain/receive_attestation_test.go
@@ -9,9 +9,7 @@ import (
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/transition"
 	testDB "github.com/prysmaticlabs/prysm/beacon-chain/db/testing"
-	"github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/protoarray"
 	"github.com/prysmaticlabs/prysm/beacon-chain/operations/attestations"
-	"github.com/prysmaticlabs/prysm/beacon-chain/state/stategen"
 	"github.com/prysmaticlabs/prysm/config/params"
 	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
 	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
@@ -42,21 +40,24 @@ func TestAttestationCheckPtState_FarFutureSlot(t *testing.T) {

 func TestVerifyLMDFFGConsistent_NotOK(t *testing.T) {
 	ctx := context.Background()
-	beaconDB := testDB.SetupDB(t)
+	opts := testServiceOptsWithDB(t)

-	cfg := &Config{BeaconDB: beaconDB, ForkChoiceStore: protoarray.New(0, 0, [32]byte{})}
-	service, err := NewService(ctx, cfg)
+	service, err := NewService(ctx, opts...)
 	require.NoError(t, err)

 	b32 := util.NewBeaconBlock()
 	b32.Block.Slot = 32
-	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(b32)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(b32)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wsb))
 	r32, err := b32.Block.HashTreeRoot()
 	require.NoError(t, err)
 	b33 := util.NewBeaconBlock()
 	b33.Block.Slot = 33
 	b33.Block.ParentRoot = r32[:]
-	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(b33)))
+	wsb, err = wrapper.WrappedSignedBeaconBlock(b33)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wsb))
 	r33, err := b33.Block.HashTreeRoot()
 	require.NoError(t, err)

@@ -70,21 +71,24 @@ func TestVerifyLMDFFGConsistent_NotOK(t *testing.T) {

 func TestVerifyLMDFFGConsistent_OK(t *testing.T) {
 	ctx := context.Background()
-	beaconDB := testDB.SetupDB(t)

-	cfg := &Config{BeaconDB: beaconDB, ForkChoiceStore: protoarray.New(0, 0, [32]byte{})}
-	service, err := NewService(ctx, cfg)
+	opts := testServiceOptsWithDB(t)
+	service, err := NewService(ctx, opts...)
 	require.NoError(t, err)

 	b32 := util.NewBeaconBlock()
 	b32.Block.Slot = 32
-	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(b32)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(b32)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wsb))
 	r32, err := b32.Block.HashTreeRoot()
 	require.NoError(t, err)
 	b33 := util.NewBeaconBlock()
 	b33.Block.Slot = 33
 	b33.Block.ParentRoot = r32[:]
-	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(b33)))
+	wsb, err = wrapper.WrappedSignedBeaconBlock(b33)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wsb))
 	r33, err := b33.Block.HashTreeRoot()
 	require.NoError(t, err)

@@ -99,17 +103,12 @@ func TestVerifyLMDFFGConsistent_OK(t *testing.T) {
 func TestProcessAttestations_Ok(t *testing.T) {
 	hook := logTest.NewGlobal()
 	ctx := context.Background()
-	beaconDB := testDB.SetupDB(t)
+	opts := testServiceOptsWithDB(t)
+	opts = append(opts, WithAttestationPool(attestations.NewPool()))

-	cfg := &Config{
-		BeaconDB:        beaconDB,
-		ForkChoiceStore: protoarray.New(0, 0, [32]byte{}),
-		StateGen:        stategen.New(beaconDB),
-		AttPool:         attestations.NewPool(),
-	}
-	service, err := NewService(ctx, cfg)
-	service.genesisTime = prysmTime.Now().Add(-1 * time.Duration(params.BeaconConfig().SecondsPerSlot) * time.Second)
+	service, err := NewService(ctx, opts...)
 	require.NoError(t, err)
+	service.genesisTime = prysmTime.Now().Add(-1 * time.Duration(params.BeaconConfig().SecondsPerSlot) * time.Second)
 	genesisState, pks := util.DeterministicGenesisState(t, 64)
 	require.NoError(t, genesisState.SetGenesisTime(uint64(prysmTime.Now().Unix())-params.BeaconConfig().SecondsPerSlot))
 	require.NoError(t, service.saveGenesisData(ctx, genesisState))
@@ -120,9 +119,45 @@ func TestProcessAttestations_Ok(t *testing.T) {
 	copied, err = transition.ProcessSlots(ctx, copied, 1)
 	require.NoError(t, err)
 	require.NoError(t, service.cfg.BeaconDB.SaveState(ctx, copied, tRoot))
-	require.NoError(t, service.cfg.ForkChoiceStore.ProcessBlock(ctx, 0, tRoot, tRoot, tRoot, 1, 1))
+	require.NoError(t, service.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx, 0, tRoot, tRoot, params.BeaconConfig().ZeroHash, 1, 1))
 	require.NoError(t, service.cfg.AttPool.SaveForkchoiceAttestations(atts))
 	service.processAttestations(ctx)
 	require.Equal(t, 0, len(service.cfg.AttPool.ForkchoiceAttestations()))
 	require.LogsDoNotContain(t, hook, "Could not process attestation for fork choice")
 }
+
+func TestNotifyEngineIfChangedHead(t *testing.T) {
+	hook := logTest.NewGlobal()
+	ctx := context.Background()
+	opts := testServiceOptsWithDB(t)
+
+	service, err := NewService(ctx, opts...)
+	require.NoError(t, err)
+
+	service.notifyEngineIfChangedHead(service.headRoot())
+	hookErr := "could not notify forkchoice update"
+	finalizedErr := "could not get finalized checkpoint"
+	require.LogsDoNotContain(t, hook, finalizedErr)
+	require.LogsDoNotContain(t, hook, hookErr)
+	service.notifyEngineIfChangedHead([32]byte{'a'})
+	require.LogsContain(t, hook, finalizedErr)
+
+	hook.Reset()
+	b := util.NewBeaconBlock()
+	b.Block.Slot = 1
+	wsb, err := wrapper.WrappedSignedBeaconBlock(b)
+	require.NoError(t, err)
+	require.NoError(t, service.cfg.BeaconDB.SaveBlock(ctx, wsb))
+	r, err := b.Block.HashTreeRoot()
+	require.NoError(t, err)
+	finalized := &ethpb.Checkpoint{Root: r[:], Epoch: 0}
+	service.head = &head{
+		slot:  1,
+		root:  r,
+		block: wsb,
+	}
+	service.store.SetFinalizedCheckpt(finalized)
+	service.notifyEngineIfChangedHead([32]byte{'b'})
+	require.LogsDoNotContain(t, hook, finalizedErr)
+	require.LogsDoNotContain(t, hook, hookErr)
+}
--- a/beacon-chain/blockchain/receive_block.go
+++ b/beacon-chain/blockchain/receive_block.go
@@ -53,14 +53,20 @@ func (s *Service) ReceiveBlock(ctx context.Context, block block.SignedBeaconBloc
 	}

 	// Reports on block and fork choice metrics.
-	reportSlotMetrics(blockCopy.Block().Slot(), s.HeadSlot(), s.CurrentSlot(), s.finalizedCheckpt)
+	finalized := s.store.FinalizedCheckpt()
+	if finalized == nil {
+		return errNilFinalizedInStore
+	}
+	reportSlotMetrics(blockCopy.Block().Slot(), s.HeadSlot(), s.CurrentSlot(), finalized)

 	// Log block sync status.
-	if err := logBlockSyncStatus(blockCopy.Block(), blockRoot, s.finalizedCheckpt, receivedTime, uint64(s.genesisTime.Unix())); err != nil {
+	if err := logBlockSyncStatus(blockCopy.Block(), blockRoot, finalized, receivedTime, uint64(s.genesisTime.Unix())); err != nil {
 		return err
 	}
 	// Log state transition data.
-	logStateTransitionData(blockCopy.Block())
+	if err := logStateTransitionData(blockCopy.Block()); err != nil {
+		return err
+	}

 	return nil
 }
@@ -98,10 +104,21 @@ func (s *Service) ReceiveBlockBatch(ctx context.Context, blocks []block.SignedBe
 		})

 		// Reports on blockCopy and fork choice metrics.
-		reportSlotMetrics(blockCopy.Block().Slot(), s.HeadSlot(), s.CurrentSlot(), s.finalizedCheckpt)
+		finalized := s.store.FinalizedCheckpt()
+		if finalized == nil {
+			return errNilFinalizedInStore
+		}
+		reportSlotMetrics(blockCopy.Block().Slot(), s.HeadSlot(), s.CurrentSlot(), finalized)
 	}

-	if err := s.VerifyWeakSubjectivityRoot(s.ctx); err != nil {
+	if err := s.cfg.BeaconDB.SaveBlocks(ctx, s.getInitSyncBlocks()); err != nil {
+		return err
+	}
+	finalized := s.store.FinalizedCheckpt()
+	if finalized == nil {
+		return errNilFinalizedInStore
+	}
+	if err := s.wsVerifier.VerifyWeakSubjectivity(s.ctx, finalized.Epoch); err != nil {
 		// log.Fatalf will prevent defer from being called
 		span.End()
 		// Exit run time if the node failed to verify weak subjectivity checkpoint.
@@ -145,8 +162,12 @@ func (s *Service) checkSaveHotStateDB(ctx context.Context) error {
 	currentEpoch := slots.ToEpoch(s.CurrentSlot())
 	// Prevent `sinceFinality` going underflow.
 	var sinceFinality types.Epoch
-	if currentEpoch > s.finalizedCheckpt.Epoch {
-		sinceFinality = currentEpoch - s.finalizedCheckpt.Epoch
+	finalized := s.store.FinalizedCheckpt()
+	if finalized == nil {
+		return errNilFinalizedInStore
+	}
+	if currentEpoch > finalized.Epoch {
+		sinceFinality = currentEpoch - finalized.Epoch
 	}

 	if sinceFinality >= epochsSinceFinalitySaveHotStateDB {
--- a/beacon-chain/blockchain/receive_block_test.go
+++ b/beacon-chain/blockchain/receive_block_test.go
@@ -33,6 +33,7 @@ func TestService_ReceiveBlock(t *testing.T) {
 		assert.NoError(t, err)
 		return blk
 	}
+	params.SetupTestConfigCleanup(t)
 	bc := params.BeaconConfig()
 	bc.ShardCommitteePeriod = 0 // Required for voluntary exits test in reasonable time.
 	params.OverrideBeaconConfig(bc)
@@ -124,29 +125,28 @@ func TestService_ReceiveBlock(t *testing.T) {
 			genesisBlockRoot := bytesutil.ToBytes32(nil)
 			require.NoError(t, beaconDB.SaveState(ctx, genesis, genesisBlockRoot))

-			cfg := &Config{
-				BeaconDB: beaconDB,
-				ForkChoiceStore: protoarray.New(
-					0, // justifiedEpoch
-					0, // finalizedEpoch
-					genesisBlockRoot,
-				),
-				AttPool:       attestations.NewPool(),
-				ExitPool:      voluntaryexits.NewPool(),
-				StateNotifier: &blockchainTesting.MockStateNotifier{RecordEvents: true},
-				StateGen:      stategen.New(beaconDB),
+			opts := []Option{
+				WithDatabase(beaconDB),
+				WithForkChoiceStore(protoarray.New(0, 0, genesisBlockRoot)),
+				WithAttestationPool(attestations.NewPool()),
+				WithExitPool(voluntaryexits.NewPool()),
+				WithStateNotifier(&blockchainTesting.MockStateNotifier{RecordEvents: true}),
+				WithStateGen(stategen.New(beaconDB)),
+				WithFinalizedStateAtStartUp(genesis),
 			}
-			s, err := NewService(ctx, cfg)
+			s, err := NewService(ctx, opts...)
 			require.NoError(t, err)
 			require.NoError(t, s.saveGenesisData(ctx, genesis))
 			gBlk, err := s.cfg.BeaconDB.GenesisBlock(ctx)
 			require.NoError(t, err)
 			gRoot, err := gBlk.Block().HashTreeRoot()
 			require.NoError(t, err)
-			s.finalizedCheckpt = &ethpb.Checkpoint{Root: gRoot[:]}
+			s.store.SetFinalizedCheckpt(&ethpb.Checkpoint{Root: gRoot[:]})
 			root, err := tt.args.block.Block.HashTreeRoot()
 			require.NoError(t, err)
-			err = s.ReceiveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(tt.args.block), root)
+			wsb, err := wrapper.WrappedSignedBeaconBlock(tt.args.block)
+			require.NoError(t, err)
+			err = s.ReceiveBlock(ctx, wsb, root)
 			if tt.wantedErr != "" {
 				assert.ErrorContains(t, tt.wantedErr, err)
 			} else {
@@ -165,32 +165,31 @@ func TestService_ReceiveBlockUpdateHead(t *testing.T) {
 	beaconDB := testDB.SetupDB(t)
 	genesisBlockRoot := bytesutil.ToBytes32(nil)
 	require.NoError(t, beaconDB.SaveState(ctx, genesis, genesisBlockRoot))
-	cfg := &Config{
-		BeaconDB: beaconDB,
-		ForkChoiceStore: protoarray.New(
-			0, // justifiedEpoch
-			0, // finalizedEpoch
-			genesisBlockRoot,
-		),
-		AttPool:       attestations.NewPool(),
-		ExitPool:      voluntaryexits.NewPool(),
-		StateNotifier: &blockchainTesting.MockStateNotifier{RecordEvents: true},
-		StateGen:      stategen.New(beaconDB),
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithForkChoiceStore(protoarray.New(0, 0, genesisBlockRoot)),
+		WithAttestationPool(attestations.NewPool()),
+		WithExitPool(voluntaryexits.NewPool()),
+		WithStateNotifier(&blockchainTesting.MockStateNotifier{RecordEvents: true}),
+		WithStateGen(stategen.New(beaconDB)),
 	}
-	s, err := NewService(ctx, cfg)
+
+	s, err := NewService(ctx, opts...)
 	require.NoError(t, err)
 	require.NoError(t, s.saveGenesisData(ctx, genesis))
 	gBlk, err := s.cfg.BeaconDB.GenesisBlock(ctx)
 	require.NoError(t, err)
 	gRoot, err := gBlk.Block().HashTreeRoot()
 	require.NoError(t, err)
-	s.finalizedCheckpt = &ethpb.Checkpoint{Root: gRoot[:]}
+	s.store.SetFinalizedCheckpt(&ethpb.Checkpoint{Root: gRoot[:]})
 	root, err := b.Block.HashTreeRoot()
 	require.NoError(t, err)
 	wg := sync.WaitGroup{}
 	wg.Add(1)
 	go func() {
-		require.NoError(t, s.ReceiveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(b), root))
+		wsb, err := wrapper.WrappedSignedBeaconBlock(b)
+		require.NoError(t, err)
+		require.NoError(t, s.ReceiveBlock(ctx, wsb, root))
 		wg.Done()
 	}()
 	wg.Wait()
@@ -198,7 +197,7 @@ func TestService_ReceiveBlockUpdateHead(t *testing.T) {
 		t.Errorf("Received %d state notifications, expected at least 1", recvd)
 	}
 	// Verify fork choice has processed the block. (Genesis block and the new block)
-	assert.Equal(t, 2, len(s.cfg.ForkChoiceStore.Nodes()))
+	assert.Equal(t, 2, s.cfg.ForkChoiceStore.NodeCount())
 }

 func TestService_ReceiveBlockBatch(t *testing.T) {
@@ -248,17 +247,13 @@ func TestService_ReceiveBlockBatch(t *testing.T) {
 			beaconDB := testDB.SetupDB(t)
 			genesisBlockRoot, err := genesis.HashTreeRoot(ctx)
 			require.NoError(t, err)
-			cfg := &Config{
-				BeaconDB: beaconDB,
-				ForkChoiceStore: protoarray.New(
-					0, // justifiedEpoch
-					0, // finalizedEpoch
-					genesisBlockRoot,
-				),
-				StateNotifier: &blockchainTesting.MockStateNotifier{RecordEvents: true},
-				StateGen:      stategen.New(beaconDB),
+			opts := []Option{
+				WithDatabase(beaconDB),
+				WithForkChoiceStore(protoarray.New(0, 0, genesisBlockRoot)),
+				WithStateNotifier(&blockchainTesting.MockStateNotifier{RecordEvents: true}),
+				WithStateGen(stategen.New(beaconDB)),
 			}
-			s, err := NewService(ctx, cfg)
+			s, err := NewService(ctx, opts...)
 			require.NoError(t, err)
 			err = s.saveGenesisData(ctx, genesis)
 			require.NoError(t, err)
@@ -267,10 +262,12 @@ func TestService_ReceiveBlockBatch(t *testing.T) {

 			gRoot, err := gBlk.Block().HashTreeRoot()
 			require.NoError(t, err)
-			s.finalizedCheckpt = &ethpb.Checkpoint{Root: gRoot[:]}
+			s.store.SetFinalizedCheckpt(&ethpb.Checkpoint{Root: gRoot[:]})
 			root, err := tt.args.block.Block.HashTreeRoot()
 			require.NoError(t, err)
-			blks := []block.SignedBeaconBlock{wrapper.WrappedPhase0SignedBeaconBlock(tt.args.block)}
+			wsb, err := wrapper.WrappedSignedBeaconBlock(tt.args.block)
+			require.NoError(t, err)
+			blks := []block.SignedBeaconBlock{wsb}
 			roots := [][32]byte{root}
 			err = s.ReceiveBlockBatch(ctx, blks, roots)
 			if tt.wantedErr != "" {
@@ -284,37 +281,41 @@ func TestService_ReceiveBlockBatch(t *testing.T) {
 }

 func TestService_HasInitSyncBlock(t *testing.T) {
-	s, err := NewService(context.Background(), &Config{StateNotifier: &blockchainTesting.MockStateNotifier{}})
+	opts := testServiceOptsNoDB()
+	opts = append(opts, WithStateNotifier(&blockchainTesting.MockStateNotifier{}))
+	s, err := NewService(context.Background(), opts...)
 	require.NoError(t, err)
 	r := [32]byte{'a'}
 	if s.HasInitSyncBlock(r) {
 		t.Error("Should not have block")
 	}
-	s.saveInitSyncBlock(r, wrapper.WrappedPhase0SignedBeaconBlock(util.NewBeaconBlock()))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(util.NewBeaconBlock())
+	require.NoError(t, err)
+	s.saveInitSyncBlock(r, wsb)
 	if !s.HasInitSyncBlock(r) {
 		t.Error("Should have block")
 	}
 }

 func TestCheckSaveHotStateDB_Enabling(t *testing.T) {
-	beaconDB := testDB.SetupDB(t)
+	opts := testServiceOptsWithDB(t)
 	hook := logTest.NewGlobal()
-	s, err := NewService(context.Background(), &Config{StateGen: stategen.New(beaconDB)})
+	s, err := NewService(context.Background(), opts...)
 	require.NoError(t, err)
 	st := params.BeaconConfig().SlotsPerEpoch.Mul(uint64(epochsSinceFinalitySaveHotStateDB))
 	s.genesisTime = time.Now().Add(time.Duration(-1*int64(st)*int64(params.BeaconConfig().SecondsPerSlot)) * time.Second)
-	s.finalizedCheckpt = &ethpb.Checkpoint{}
+	s.store.SetFinalizedCheckpt(&ethpb.Checkpoint{})

 	require.NoError(t, s.checkSaveHotStateDB(context.Background()))
 	assert.LogsContain(t, hook, "Entering mode to save hot states in DB")
 }

 func TestCheckSaveHotStateDB_Disabling(t *testing.T) {
-	beaconDB := testDB.SetupDB(t)
 	hook := logTest.NewGlobal()
-	s, err := NewService(context.Background(), &Config{StateGen: stategen.New(beaconDB)})
+	opts := testServiceOptsWithDB(t)
+	s, err := NewService(context.Background(), opts...)
 	require.NoError(t, err)
-	s.finalizedCheckpt = &ethpb.Checkpoint{}
+	s.store.SetFinalizedCheckpt(&ethpb.Checkpoint{})
 	require.NoError(t, s.checkSaveHotStateDB(context.Background()))
 	s.genesisTime = time.Now()

@@ -323,11 +324,11 @@ func TestCheckSaveHotStateDB_Disabling(t *testing.T) {
 }

 func TestCheckSaveHotStateDB_Overflow(t *testing.T) {
-	beaconDB := testDB.SetupDB(t)
 	hook := logTest.NewGlobal()
-	s, err := NewService(context.Background(), &Config{StateGen: stategen.New(beaconDB)})
+	opts := testServiceOptsWithDB(t)
+	s, err := NewService(context.Background(), opts...)
 	require.NoError(t, err)
-	s.finalizedCheckpt = &ethpb.Checkpoint{Epoch: 10000000}
+	s.store.SetFinalizedCheckpt(&ethpb.Checkpoint{Epoch: 10000000})
 	s.genesisTime = time.Now()

 	require.NoError(t, s.checkSaveHotStateDB(context.Background()))
--- a/beacon-chain/blockchain/service.go
+++ b/beacon-chain/blockchain/service.go
@@ -3,6 +3,7 @@
 package blockchain

 import (
+	"bytes"
 	"context"
 	"fmt"
 	"runtime"
@@ -12,6 +13,7 @@ import (
 	"github.com/pkg/errors"
 	types "github.com/prysmaticlabs/eth2-types"
 	"github.com/prysmaticlabs/prysm/async/event"
+	"github.com/prysmaticlabs/prysm/beacon-chain/blockchain/store"
 	"github.com/prysmaticlabs/prysm/beacon-chain/cache"
 	"github.com/prysmaticlabs/prysm/beacon-chain/cache/depositcache"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/feed"
@@ -20,19 +22,23 @@ import (
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/transition"
 	"github.com/prysmaticlabs/prysm/beacon-chain/db"
 	f "github.com/prysmaticlabs/prysm/beacon-chain/forkchoice"
+	doublylinkedtree "github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/doubly-linked-tree"
 	"github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/protoarray"
 	"github.com/prysmaticlabs/prysm/beacon-chain/operations/attestations"
 	"github.com/prysmaticlabs/prysm/beacon-chain/operations/slashings"
 	"github.com/prysmaticlabs/prysm/beacon-chain/operations/voluntaryexits"
 	"github.com/prysmaticlabs/prysm/beacon-chain/p2p"
 	"github.com/prysmaticlabs/prysm/beacon-chain/powchain"
+	enginev1 "github.com/prysmaticlabs/prysm/beacon-chain/powchain/engine-api-client/v1"
 	"github.com/prysmaticlabs/prysm/beacon-chain/state"
 	"github.com/prysmaticlabs/prysm/beacon-chain/state/stategen"
 	"github.com/prysmaticlabs/prysm/cmd/beacon-chain/flags"
+	"github.com/prysmaticlabs/prysm/config/features"
 	"github.com/prysmaticlabs/prysm/config/params"
 	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
 	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
 	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/block"
+	prysmTime "github.com/prysmaticlabs/prysm/time"
 	"github.com/prysmaticlabs/prysm/time/slots"
 	"github.com/sirupsen/logrus"
 	"go.opencensus.io/trace"
@@ -45,30 +51,26 @@ const headSyncMinEpochsAfterCheckpoint = 128
 // Service represents a service that handles the internal
 // logic of managing the full PoS beacon chain.
 type Service struct {
-	cfg                   *Config
-	ctx                   context.Context
-	cancel                context.CancelFunc
-	genesisTime           time.Time
-	head                  *head
-	headLock              sync.RWMutex
-	genesisRoot           [32]byte
-	justifiedCheckpt      *ethpb.Checkpoint
-	prevJustifiedCheckpt  *ethpb.Checkpoint
-	bestJustifiedCheckpt  *ethpb.Checkpoint
-	finalizedCheckpt      *ethpb.Checkpoint
-	prevFinalizedCheckpt  *ethpb.Checkpoint
+	cfg         *config
+	ctx         context.Context
+	cancel      context.CancelFunc
+	genesisTime time.Time
+	head        *head
+	headLock    sync.RWMutex
+	// originBlockRoot is the genesis root, or weak subjectivity checkpoint root, depending on how the node is initialized
+	originBlockRoot       [32]byte
 	nextEpochBoundarySlot types.Slot
 	boundaryRoots         [][32]byte
 	checkpointStateCache  *cache.CheckpointStateCache
 	initSyncBlocks        map[[32]byte]block.SignedBeaconBlock
 	initSyncBlocksLock    sync.RWMutex
-	justifiedBalances     []uint64
-	justifiedBalancesLock sync.RWMutex
-	wsVerified            bool
+	justifiedBalances     *stateBalanceCache
+	wsVerifier            *WeakSubjectivityVerifier
+	store                 *store.Store
 }

-// Config options for the service.
-type Config struct {
+// config options for the service.
+type config struct {
 	BeaconBlockBuf          int
 	ChainStartFetcher       powchain.ChainStartFetcher
 	BeaconDB                db.HeadAccessDatabase
@@ -84,165 +86,309 @@ type Config struct {
 	StateGen                *stategen.State
 	SlasherAttestationsFeed *event.Feed
 	WeakSubjectivityCheckpt *ethpb.Checkpoint
+	BlockFetcher            powchain.POWBlockFetcher
+	FinalizedStateAtStartUp state.BeaconState
+	ExecutionEngineCaller   enginev1.Caller
 }

 // NewService instantiates a new block service instance that will
 // be registered into a running beacon node.
-func NewService(ctx context.Context, cfg *Config) (*Service, error) {
+func NewService(ctx context.Context, opts ...Option) (*Service, error) {
 	ctx, cancel := context.WithCancel(ctx)
-	return &Service{
-		cfg:                  cfg,
+	srv := &Service{
 		ctx:                  ctx,
 		cancel:               cancel,
 		boundaryRoots:        [][32]byte{},
 		checkpointStateCache: cache.NewCheckpointStateCache(),
 		initSyncBlocks:       make(map[[32]byte]block.SignedBeaconBlock),
-		justifiedBalances:    make([]uint64, 0),
-	}, nil
+		cfg:                  &config{},
+		store:                &store.Store{},
+	}
+	for _, opt := range opts {
+		if err := opt(srv); err != nil {
+			return nil, err
+		}
+	}
+	var err error
+	if srv.justifiedBalances == nil {
+		srv.justifiedBalances, err = newStateBalanceCache(srv.cfg.StateGen)
+		if err != nil {
+			return nil, err
+		}
+	}
+	srv.wsVerifier, err = NewWeakSubjectivityVerifier(srv.cfg.WeakSubjectivityCheckpt, srv.cfg.BeaconDB)
+	if err != nil {
+		return nil, err
+	}
+	return srv, nil
 }

 // Start a blockchain service's main event loop.
 func (s *Service) Start() {
-	// For running initial sync with state cache, in an event of restart, we use
-	// last finalized check point as start point to sync instead of head
-	// state. This is because we no longer save state every slot during sync.
-	cp, err := s.cfg.BeaconDB.FinalizedCheckpoint(s.ctx)
-	if err != nil {
-		log.Fatalf("Could not fetch finalized cp: %v", err)
-	}
+	saved := s.cfg.FinalizedStateAtStartUp

-	r := bytesutil.ToBytes32(cp.Root)
-	// Before the first finalized epoch, in the current epoch,
-	// the finalized root is defined as zero hashes instead of genesis root hash.
-	// We want to use genesis root to retrieve for state.
-	if r == params.BeaconConfig().ZeroHash {
-		genesisBlock, err := s.cfg.BeaconDB.GenesisBlock(s.ctx)
-		if err != nil {
-			log.Fatalf("Could not fetch finalized cp: %v", err)
+	if saved != nil && !saved.IsNil() {
+		if err := s.StartFromSavedState(saved); err != nil {
+			log.Fatal(err)
 		}
-		if genesisBlock != nil && !genesisBlock.IsNil() {
-			r, err = genesisBlock.Block().HashTreeRoot()
-			if err != nil {
-				log.Fatalf("Could not tree hash genesis block: %v", err)
-			}
-		}
-	}
-	beaconState, err := s.cfg.StateGen.StateByRoot(s.ctx, r)
-	if err != nil {
-		log.Fatalf("Could not fetch beacon state by root: %v", err)
-	}
-
-	// Make sure that attestation processor is subscribed and ready for state initializing event.
-	attestationProcessorSubscribed := make(chan struct{}, 1)
-
-	// If the chain has already been initialized, simply start the block processing routine.
-	if beaconState != nil && !beaconState.IsNil() {
-		log.Info("Blockchain data already exists in DB, initializing...")
-		s.genesisTime = time.Unix(int64(beaconState.GenesisTime()), 0)
-		s.cfg.AttService.SetGenesisTime(beaconState.GenesisTime())
-		if err := s.initializeChainInfo(s.ctx); err != nil {
-			log.Fatalf("Could not set up chain info: %v", err)
-		}
-
-		// We start a counter to genesis, if needed.
-		gState, err := s.cfg.BeaconDB.GenesisState(s.ctx)
-		if err != nil {
-			log.Fatalf("Could not retrieve genesis state: %v", err)
-		}
-		gRoot, err := gState.HashTreeRoot(s.ctx)
-		if err != nil {
-			log.Fatalf("Could not hash tree root genesis state: %v", err)
-		}
-		go slots.CountdownToGenesis(s.ctx, s.genesisTime, uint64(gState.NumValidators()), gRoot)
-
-		justifiedCheckpoint, err := s.cfg.BeaconDB.JustifiedCheckpoint(s.ctx)
-		if err != nil {
-			log.Fatalf("Could not get justified checkpoint: %v", err)
-		}
-		finalizedCheckpoint, err := s.cfg.BeaconDB.FinalizedCheckpoint(s.ctx)
-		if err != nil {
-			log.Fatalf("Could not get finalized checkpoint: %v", err)
-		}
-
-		// Resume fork choice.
-		s.justifiedCheckpt = ethpb.CopyCheckpoint(justifiedCheckpoint)
-		if err := s.cacheJustifiedStateBalances(s.ctx, s.ensureRootNotZeros(bytesutil.ToBytes32(s.justifiedCheckpt.Root))); err != nil {
-			log.Fatalf("Could not cache justified state balances: %v", err)
-		}
-		s.prevJustifiedCheckpt = ethpb.CopyCheckpoint(justifiedCheckpoint)
-		s.bestJustifiedCheckpt = ethpb.CopyCheckpoint(justifiedCheckpoint)
-		s.finalizedCheckpt = ethpb.CopyCheckpoint(finalizedCheckpoint)
-		s.prevFinalizedCheckpt = ethpb.CopyCheckpoint(finalizedCheckpoint)
-		s.resumeForkChoice(justifiedCheckpoint, finalizedCheckpoint)
-
-		ss, err := slots.EpochStart(s.finalizedCheckpt.Epoch)
-		if err != nil {
-			log.Fatalf("Could not get start slot of finalized epoch: %v", err)
-		}
-		h := s.headBlock().Block()
-		if h.Slot() > ss {
-			log.WithFields(logrus.Fields{
-				"startSlot": ss,
-				"endSlot":   h.Slot(),
-			}).Info("Loading blocks to fork choice store, this may take a while.")
-			if err := s.fillInForkChoiceMissingBlocks(s.ctx, h, s.finalizedCheckpt, s.justifiedCheckpt); err != nil {
-				log.Fatalf("Could not fill in fork choice store missing blocks: %v", err)
-			}
-		}
-
-		if err := s.VerifyWeakSubjectivityRoot(s.ctx); err != nil {
-			// Exit run time if the node failed to verify weak subjectivity checkpoint.
-			log.Fatalf("Could not verify weak subjectivity checkpoint: %v", err)
-		}
-
-		s.cfg.StateNotifier.StateFeed().Send(&feed.Event{
-			Type: statefeed.Initialized,
-			Data: &statefeed.InitializedData{
-				StartTime:             s.genesisTime,
-				GenesisValidatorsRoot: beaconState.GenesisValidatorRoot(),
-			},
-		})
 	} else {
-		log.Info("Waiting to reach the validator deposit threshold to start the beacon chain...")
-		if s.cfg.ChainStartFetcher == nil {
-			log.Fatal("Not configured web3Service for POW chain")
-			return // return need for TestStartUninitializedChainWithoutConfigPOWChain.
+		if err := s.startFromPOWChain(); err != nil {
+			log.Fatal(err)
 		}
-		go func() {
-			stateChannel := make(chan *feed.Event, 1)
-			stateSub := s.cfg.StateNotifier.StateFeed().Subscribe(stateChannel)
-			defer stateSub.Unsubscribe()
-			<-attestationProcessorSubscribed
-			for {
-				select {
-				case event := <-stateChannel:
-					if event.Type == statefeed.ChainStarted {
-						data, ok := event.Data.(*statefeed.ChainStartedData)
-						if !ok {
-							log.Error("event data is not type *statefeed.ChainStartedData")
-							return
-						}
-						log.WithField("starttime", data.StartTime).Debug("Received chain start event")
-						s.processChainStartTime(s.ctx, data.StartTime)
-						return
-					}
-				case <-s.ctx.Done():
-					log.Debug("Context closed, exiting goroutine")
-					return
-				case err := <-stateSub.Err():
-					log.WithError(err).Error("Subscription to state notifier failed")
-					return
-				}
-			}
-		}()
 	}
-
-	go s.processAttestationsRoutine(attestationProcessorSubscribed)
+	s.spawnProcessAttestationsRoutine(s.cfg.StateNotifier.StateFeed())
 }

-// processChainStartTime initializes a series of deposits from the ChainStart deposits in the eth1
+// Stop the blockchain service's main event loop and associated goroutines.
+func (s *Service) Stop() error {
+	defer s.cancel()
+
+	if s.cfg.StateGen != nil && s.head != nil && s.head.state != nil {
+		if err := s.cfg.StateGen.ForceCheckpoint(s.ctx, s.head.state.FinalizedCheckpoint().Root); err != nil {
+			return err
+		}
+	}
+
+	// Save initial sync cached blocks to the DB before stop.
+	return s.cfg.BeaconDB.SaveBlocks(s.ctx, s.getInitSyncBlocks())
+}
+
+// Status always returns nil unless there is an error condition that causes
+// this service to be unhealthy.
+func (s *Service) Status() error {
+	if s.originBlockRoot == params.BeaconConfig().ZeroHash {
+		return errors.New("genesis state has not been created")
+	}
+	if runtime.NumGoroutine() > s.cfg.MaxRoutines {
+		return fmt.Errorf("too many goroutines %d", runtime.NumGoroutine())
+	}
+	return nil
+}
+
+func (s *Service) StartFromSavedState(saved state.BeaconState) error {
+	log.Info("Blockchain data already exists in DB, initializing...")
+	s.genesisTime = time.Unix(int64(saved.GenesisTime()), 0) // lint:ignore uintcast -- Genesis time will not exceed int64 in your lifetime.
+	s.cfg.AttService.SetGenesisTime(saved.GenesisTime())
+
+	originRoot, err := s.originRootFromSavedState(s.ctx)
+	if err != nil {
+		return err
+	}
+	s.originBlockRoot = originRoot
+
+	if err := s.initializeHeadFromDB(s.ctx); err != nil {
+		return errors.Wrap(err, "could not set up chain info")
+	}
+	spawnCountdownIfPreGenesis(s.ctx, s.genesisTime, s.cfg.BeaconDB)
+
+	justified, err := s.cfg.BeaconDB.JustifiedCheckpoint(s.ctx)
+	if err != nil {
+		return errors.Wrap(err, "could not get justified checkpoint")
+	}
+	finalized, err := s.cfg.BeaconDB.FinalizedCheckpoint(s.ctx)
+	if err != nil {
+		return errors.Wrap(err, "could not get finalized checkpoint")
+	}
+	s.store = store.New(justified, finalized)
+
+	var store f.ForkChoicer
+	fRoot := bytesutil.ToBytes32(finalized.Root)
+	if features.Get().EnableForkChoiceDoublyLinkedTree {
+		store = doublylinkedtree.New(justified.Epoch, finalized.Epoch)
+	} else {
+		store = protoarray.New(justified.Epoch, finalized.Epoch, fRoot)
+	}
+	s.cfg.ForkChoiceStore = store
+	fb, err := s.cfg.BeaconDB.Block(s.ctx, s.ensureRootNotZeros(fRoot))
+	if err != nil {
+		return errors.Wrap(err, "could not get finalized checkpoint block")
+	}
+	if fb == nil {
+		return errNilFinalizedInStore
+	}
+	payloadHash, err := getBlockPayloadHash(fb.Block())
+	if err != nil {
+		return errors.Wrap(err, "could not get execution payload hash")
+	}
+	fSlot := fb.Block().Slot()
+	if err := store.InsertOptimisticBlock(s.ctx, fSlot, fRoot, params.BeaconConfig().ZeroHash,
+		payloadHash, justified.Epoch, finalized.Epoch); err != nil {
+		return errors.Wrap(err, "could not insert finalized block to forkchoice")
+	}
+
+	lastValidatedCheckpoint, err := s.cfg.BeaconDB.LastValidatedCheckpoint(s.ctx)
+	if err != nil {
+		return errors.Wrap(err, "could not get last validated checkpoint")
+	}
+	if bytes.Equal(finalized.Root, lastValidatedCheckpoint.Root) {
+		if err := store.SetOptimisticToValid(s.ctx, fRoot); err != nil {
+			return errors.Wrap(err, "could not set finalized block as validated")
+		}
+	}
+
+	h := s.headBlock().Block()
+	if h.Slot() > fSlot {
+		log.WithFields(logrus.Fields{
+			"startSlot": fSlot,
+			"endSlot":   h.Slot(),
+		}).Info("Loading blocks to fork choice store, this may take a while.")
+		if err := s.fillInForkChoiceMissingBlocks(s.ctx, h, finalized, justified); err != nil {
+			return errors.Wrap(err, "could not fill in fork choice store missing blocks")
+		}
+	}
+
+	// not attempting to save initial sync blocks here, because there shouldn't be any until
+	// after the statefeed.Initialized event is fired (below)
+	if err := s.wsVerifier.VerifyWeakSubjectivity(s.ctx, finalized.Epoch); err != nil {
+		// Exit run time if the node failed to verify weak subjectivity checkpoint.
+		return errors.Wrap(err, "could not verify initial checkpoint provided for chain sync")
+	}
+
+	s.cfg.StateNotifier.StateFeed().Send(&feed.Event{
+		Type: statefeed.Initialized,
+		Data: &statefeed.InitializedData{
+			StartTime:             s.genesisTime,
+			GenesisValidatorsRoot: saved.GenesisValidatorsRoot(),
+		},
+	})
+
+	return nil
+}
+
+func (s *Service) originRootFromSavedState(ctx context.Context) ([32]byte, error) {
+	// first check if we have started from checkpoint sync and have a root
+	originRoot, err := s.cfg.BeaconDB.OriginCheckpointBlockRoot(ctx)
+	if err == nil {
+		return originRoot, nil
+	}
+	if !errors.Is(err, db.ErrNotFound) {
+		return originRoot, errors.Wrap(err, "could not retrieve checkpoint sync chain origin data from db")
+	}
+
+	// we got here because OriginCheckpointBlockRoot gave us an ErrNotFound. this means the node was started from a genesis state,
+	// so we should have a value for GenesisBlock
+	genesisBlock, err := s.cfg.BeaconDB.GenesisBlock(ctx)
+	if err != nil {
+		return originRoot, errors.Wrap(err, "could not get genesis block from db")
+	}
+	if err := helpers.BeaconBlockIsNil(genesisBlock); err != nil {
+		return originRoot, err
+	}
+	genesisBlkRoot, err := genesisBlock.Block().HashTreeRoot()
+	if err != nil {
+		return genesisBlkRoot, errors.Wrap(err, "could not get signing root of genesis block")
+	}
+	return genesisBlkRoot, nil
+}
+
+// initializeHeadFromDB uses the finalized checkpoint and head block found in the database to set the current head
+// note that this may block until stategen replays blocks between the finalized and head blocks
+// if the head sync flag was specified and the gap between the finalized and head blocks is at least 128 epochs long
+func (s *Service) initializeHeadFromDB(ctx context.Context) error {
+	finalized, err := s.cfg.BeaconDB.FinalizedCheckpoint(ctx)
+	if err != nil {
+		return errors.Wrap(err, "could not get finalized checkpoint from db")
+	}
+	if finalized == nil {
+		// This should never happen. At chain start, the finalized checkpoint
+		// would be the genesis state and block.
+		return errors.New("no finalized epoch in the database")
+	}
+	finalizedRoot := s.ensureRootNotZeros(bytesutil.ToBytes32(finalized.Root))
+	var finalizedState state.BeaconState
+
+	finalizedState, err = s.cfg.StateGen.Resume(ctx, s.cfg.FinalizedStateAtStartUp)
+	if err != nil {
+		return errors.Wrap(err, "could not get finalized state from db")
+	}
+
+	if flags.Get().HeadSync {
+		headBlock, err := s.cfg.BeaconDB.HeadBlock(ctx)
+		if err != nil {
+			return errors.Wrap(err, "could not retrieve head block")
+		}
+		headEpoch := slots.ToEpoch(headBlock.Block().Slot())
+		var epochsSinceFinality types.Epoch
+		if headEpoch > finalized.Epoch {
+			epochsSinceFinality = headEpoch - finalized.Epoch
+		}
+		// Head sync when node is far enough beyond known finalized epoch,
+		// this becomes really useful during long period of non-finality.
+		if epochsSinceFinality >= headSyncMinEpochsAfterCheckpoint {
+			headRoot, err := headBlock.Block().HashTreeRoot()
+			if err != nil {
+				return errors.Wrap(err, "could not hash head block")
+			}
+			finalizedState, err := s.cfg.StateGen.Resume(ctx, s.cfg.FinalizedStateAtStartUp)
+			if err != nil {
+				return errors.Wrap(err, "could not get finalized state from db")
+			}
+			log.Infof("Regenerating state from the last checkpoint at slot %d to current head slot of %d."+
+				"This process may take a while, please wait.", finalizedState.Slot(), headBlock.Block().Slot())
+			headState, err := s.cfg.StateGen.StateByRoot(ctx, headRoot)
+			if err != nil {
+				return errors.Wrap(err, "could not retrieve head state")
+			}
+			s.setHead(headRoot, headBlock, headState)
+			return nil
+		} else {
+			log.Warnf("Finalized checkpoint at slot %d is too close to the current head slot, "+
+				"resetting head from the checkpoint ('--%s' flag is ignored).",
+				finalizedState.Slot(), flags.HeadSync.Name)
+		}
+	}
+
+	finalizedBlock, err := s.cfg.BeaconDB.Block(ctx, finalizedRoot)
+	if err != nil {
+		return errors.Wrap(err, "could not get finalized block from db")
+	}
+
+	if finalizedState == nil || finalizedState.IsNil() || finalizedBlock == nil || finalizedBlock.IsNil() {
+		return errors.New("finalized state and block can't be nil")
+	}
+	s.setHead(finalizedRoot, finalizedBlock, finalizedState)
+
+	return nil
+}
+
+func (s *Service) startFromPOWChain() error {
+	log.Info("Waiting to reach the validator deposit threshold to start the beacon chain...")
+	if s.cfg.ChainStartFetcher == nil {
+		return errors.New("not configured web3Service for POW chain")
+	}
+	go func() {
+		stateChannel := make(chan *feed.Event, 1)
+		stateSub := s.cfg.StateNotifier.StateFeed().Subscribe(stateChannel)
+		defer stateSub.Unsubscribe()
+		for {
+			select {
+			case event := <-stateChannel:
+				if event.Type == statefeed.ChainStarted {
+					data, ok := event.Data.(*statefeed.ChainStartedData)
+					if !ok {
+						log.Error("event data is not type *statefeed.ChainStartedData")
+						return
+					}
+					log.WithField("starttime", data.StartTime).Debug("Received chain start event")
+					s.onPowchainStart(s.ctx, data.StartTime)
+					return
+				}
+			case <-s.ctx.Done():
+				log.Debug("Context closed, exiting goroutine")
+				return
+			case err := <-stateSub.Err():
+				log.WithError(err).Error("Subscription to state notifier failed")
+				return
+			}
+		}
+	}()
+
+	return nil
+}
+
+// onPowchainStart initializes a series of deposits from the ChainStart deposits in the eth1
 // deposit contract, initializes the beacon chain's state, and kicks off the beacon chain.
-func (s *Service) processChainStartTime(ctx context.Context, genesisTime time.Time) {
+func (s *Service) onPowchainStart(ctx context.Context, genesisTime time.Time) {
 	preGenesisState := s.cfg.ChainStartFetcher.PreGenesisState()
 	initializedState, err := s.initializeBeaconChain(ctx, genesisTime, preGenesisState, s.cfg.ChainStartFetcher.ChainStartEth1Data())
 	if err != nil {
@@ -261,7 +407,7 @@ func (s *Service) processChainStartTime(ctx context.Context, genesisTime time.Ti
 		Type: statefeed.Initialized,
 		Data: &statefeed.InitializedData{
 			StartTime:             genesisTime,
-			GenesisValidatorsRoot: initializedState.GenesisValidatorRoot(),
+			GenesisValidatorsRoot: initializedState.GenesisValidatorsRoot(),
 		},
 	})
 }
@@ -306,32 +452,6 @@ func (s *Service) initializeBeaconChain(
 	return genesisState, nil
 }

-// Stop the blockchain service's main event loop and associated goroutines.
-func (s *Service) Stop() error {
-	defer s.cancel()
-
-	if s.cfg.StateGen != nil && s.head != nil && s.head.state != nil {
-		if err := s.cfg.StateGen.ForceCheckpoint(s.ctx, s.head.state.FinalizedCheckpoint().Root); err != nil {
-			return err
-		}
-	}
-
-	// Save initial sync cached blocks to the DB before stop.
-	return s.cfg.BeaconDB.SaveBlocks(s.ctx, s.getInitSyncBlocks())
-}
-
-// Status always returns nil unless there is an error condition that causes
-// this service to be unhealthy.
-func (s *Service) Status() error {
-	if s.genesisRoot == params.BeaconConfig().ZeroHash {
-		return errors.New("genesis state has not been created")
-	}
-	if runtime.NumGoroutine() > s.cfg.MaxRoutines {
-		return fmt.Errorf("too many goroutines %d", runtime.NumGoroutine())
-	}
-	return nil
-}
-
 // This gets called when beacon chain is first initialized to save genesis data (state, block, and more) in db.
 func (s *Service) saveGenesisData(ctx context.Context, genesisState state.BeaconState) error {
 	if err := s.cfg.BeaconDB.SaveGenesisData(ctx, genesisState); err != nil {
@@ -346,123 +466,34 @@ func (s *Service) saveGenesisData(ctx context.Context, genesisState state.Beacon
 		return errors.Wrap(err, "could not get genesis block root")
 	}

-	s.genesisRoot = genesisBlkRoot
+	s.originBlockRoot = genesisBlkRoot
 	s.cfg.StateGen.SaveFinalizedState(0 /*slot*/, genesisBlkRoot, genesisState)

 	// Finalized checkpoint at genesis is a zero hash.
 	genesisCheckpoint := genesisState.FinalizedCheckpoint()
+	s.store = store.New(genesisCheckpoint, genesisCheckpoint)

-	s.justifiedCheckpt = ethpb.CopyCheckpoint(genesisCheckpoint)
-	if err := s.cacheJustifiedStateBalances(ctx, genesisBlkRoot); err != nil {
+	payloadHash, err := getBlockPayloadHash(genesisBlk.Block())
+	if err != nil {
 		return err
 	}
-	s.prevJustifiedCheckpt = ethpb.CopyCheckpoint(genesisCheckpoint)
-	s.bestJustifiedCheckpt = ethpb.CopyCheckpoint(genesisCheckpoint)
-	s.finalizedCheckpt = ethpb.CopyCheckpoint(genesisCheckpoint)
-	s.prevFinalizedCheckpt = ethpb.CopyCheckpoint(genesisCheckpoint)
-
-	if err := s.cfg.ForkChoiceStore.ProcessBlock(ctx,
+	if err := s.cfg.ForkChoiceStore.InsertOptimisticBlock(ctx,
 		genesisBlk.Block().Slot(),
 		genesisBlkRoot,
 		params.BeaconConfig().ZeroHash,
-		[32]byte{},
+		payloadHash,
 		genesisCheckpoint.Epoch,
 		genesisCheckpoint.Epoch); err != nil {
 		log.Fatalf("Could not process genesis block for fork choice: %v", err)
 	}
+	if err := s.cfg.ForkChoiceStore.SetOptimisticToValid(ctx, genesisBlkRoot); err != nil {
+		log.Fatalf("Could not set optimistic status of genesis block to false: %v", err)
+	}

 	s.setHead(genesisBlkRoot, genesisBlk, genesisState)
 	return nil
 }

-// This gets called to initialize chain info variables using the finalized checkpoint stored in DB
-func (s *Service) initializeChainInfo(ctx context.Context) error {
-	genesisBlock, err := s.cfg.BeaconDB.GenesisBlock(ctx)
-	if err != nil {
-		return errors.Wrap(err, "could not get genesis block from db")
-	}
-	if genesisBlock == nil || genesisBlock.IsNil() {
-		return errors.New("no genesis block in db")
-	}
-	genesisBlkRoot, err := genesisBlock.Block().HashTreeRoot()
-	if err != nil {
-		return errors.Wrap(err, "could not get signing root of genesis block")
-	}
-	s.genesisRoot = genesisBlkRoot
-
-	finalized, err := s.cfg.BeaconDB.FinalizedCheckpoint(ctx)
-	if err != nil {
-		return errors.Wrap(err, "could not get finalized checkpoint from db")
-	}
-	if finalized == nil {
-		// This should never happen. At chain start, the finalized checkpoint
-		// would be the genesis state and block.
-		return errors.New("no finalized epoch in the database")
-	}
-	finalizedRoot := s.ensureRootNotZeros(bytesutil.ToBytes32(finalized.Root))
-	var finalizedState state.BeaconState
-
-	finalizedState, err = s.cfg.StateGen.Resume(ctx)
-	if err != nil {
-		return errors.Wrap(err, "could not get finalized state from db")
-	}
-
-	if flags.Get().HeadSync {
-		headBlock, err := s.cfg.BeaconDB.HeadBlock(ctx)
-		if err != nil {
-			return errors.Wrap(err, "could not retrieve head block")
-		}
-		headEpoch := slots.ToEpoch(headBlock.Block().Slot())
-		var epochsSinceFinality types.Epoch
-		if headEpoch > finalized.Epoch {
-			epochsSinceFinality = headEpoch - finalized.Epoch
-		}
-		// Head sync when node is far enough beyond known finalized epoch,
-		// this becomes really useful during long period of non-finality.
-		if epochsSinceFinality >= headSyncMinEpochsAfterCheckpoint {
-			headRoot, err := headBlock.Block().HashTreeRoot()
-			if err != nil {
-				return errors.Wrap(err, "could not hash head block")
-			}
-			finalizedState, err := s.cfg.StateGen.Resume(ctx)
-			if err != nil {
-				return errors.Wrap(err, "could not get finalized state from db")
-			}
-			log.Infof("Regenerating state from the last checkpoint at slot %d to current head slot of %d."+
-				"This process may take a while, please wait.", finalizedState.Slot(), headBlock.Block().Slot())
-			headState, err := s.cfg.StateGen.StateByRoot(ctx, headRoot)
-			if err != nil {
-				return errors.Wrap(err, "could not retrieve head state")
-			}
-			s.setHead(headRoot, headBlock, headState)
-			return nil
-		} else {
-			log.Warnf("Finalized checkpoint at slot %d is too close to the current head slot, "+
-				"resetting head from the checkpoint ('--%s' flag is ignored).",
-				finalizedState.Slot(), flags.HeadSync.Name)
-		}
-	}
-
-	finalizedBlock, err := s.cfg.BeaconDB.Block(ctx, finalizedRoot)
-	if err != nil {
-		return errors.Wrap(err, "could not get finalized block from db")
-	}
-
-	if finalizedState == nil || finalizedState.IsNil() || finalizedBlock == nil || finalizedBlock.IsNil() {
-		return errors.New("finalized state and block can't be nil")
-	}
-	s.setHead(finalizedRoot, finalizedBlock, finalizedState)
-
-	return nil
-}
-
-// This is called when a client starts from non-genesis slot. This passes last justified and finalized
-// information to fork choice service to initializes fork choice store.
-func (s *Service) resumeForkChoice(justifiedCheckpoint, finalizedCheckpoint *ethpb.Checkpoint) {
-	store := protoarray.New(justifiedCheckpoint.Epoch, finalizedCheckpoint.Epoch, bytesutil.ToBytes32(finalizedCheckpoint.Root))
-	s.cfg.ForkChoiceStore = store
-}
-
 // This returns true if block has been processed before. Two ways to verify the block has been processed:
 // 1.) Check fork choice store.
 // 2.) Check DB.
@@ -474,3 +505,20 @@ func (s *Service) hasBlock(ctx context.Context, root [32]byte) bool {

 	return s.cfg.BeaconDB.HasBlock(ctx, root)
 }
+
+func spawnCountdownIfPreGenesis(ctx context.Context, genesisTime time.Time, db db.HeadAccessDatabase) {
+	currentTime := prysmTime.Now()
+	if currentTime.After(genesisTime) {
+		return
+	}
+
+	gState, err := db.GenesisState(ctx)
+	if err != nil {
+		log.Fatalf("Could not retrieve genesis state: %v", err)
+	}
+	gRoot, err := gState.HashTreeRoot(ctx)
+	if err != nil {
+		log.Fatalf("Could not hash tree root genesis state: %v", err)
+	}
+	go slots.CountdownToGenesis(ctx, genesisTime, uint64(gState.NumValidators()), gRoot)
+}
--- a/beacon-chain/blockchain/service_norace_test.go
+++ b/beacon-chain/blockchain/service_norace_test.go
@@ -18,7 +18,7 @@ func init() {
 func TestChainService_SaveHead_DataRace(t *testing.T) {
 	beaconDB := testDB.SetupDB(t)
 	s := &Service{
-		cfg: &Config{BeaconDB: beaconDB},
+		cfg: &config{BeaconDB: beaconDB},
 	}
 	go func() {
 		require.NoError(t, s.saveHead(context.Background(), [32]byte{}))
--- a/beacon-chain/blockchain/service_test.go
+++ b/beacon-chain/blockchain/service_test.go
@@ -9,6 +9,8 @@ import (

 	"github.com/ethereum/go-ethereum/common"
 	"github.com/prysmaticlabs/prysm/async/event"
+	"github.com/prysmaticlabs/prysm/beacon-chain/blockchain/store"
+	mock "github.com/prysmaticlabs/prysm/beacon-chain/blockchain/testing"
 	"github.com/prysmaticlabs/prysm/beacon-chain/cache/depositcache"
 	b "github.com/prysmaticlabs/prysm/beacon-chain/core/blocks"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/feed"
@@ -17,6 +19,7 @@ import (
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/transition"
 	"github.com/prysmaticlabs/prysm/beacon-chain/db"
 	testDB "github.com/prysmaticlabs/prysm/beacon-chain/db/testing"
+	doublylinkedtree "github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/doubly-linked-tree"
 	"github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/protoarray"
 	"github.com/prysmaticlabs/prysm/beacon-chain/operations/attestations"
 	"github.com/prysmaticlabs/prysm/beacon-chain/p2p"
@@ -94,11 +97,12 @@ func setupBeaconChain(t *testing.T, beaconDB db.Database) *Service {
 		DepositContainers: []*ethpb.DepositContainer{},
 	})
 	require.NoError(t, err)
-	web3Service, err = powchain.NewService(ctx, &powchain.Web3ServiceConfig{
-		BeaconDB:        beaconDB,
-		HttpEndpoints:   []string{endpoint},
-		DepositContract: common.Address{},
-	})
+	web3Service, err = powchain.NewService(
+		ctx,
+		powchain.WithDatabase(beaconDB),
+		powchain.WithHttpEndpoints([]string{endpoint}),
+		powchain.WithDepositContractAddress(common.Address{}),
+	)
 	require.NoError(t, err, "Unable to set up web3 service")

 	attService, err := attestations.NewService(ctx, &attestations.Config{Pool: attestations.NewPool()})
@@ -107,23 +111,23 @@ func setupBeaconChain(t *testing.T, beaconDB db.Database) *Service {
 	depositCache, err := depositcache.New()
 	require.NoError(t, err)

-	cfg := &Config{
-		BeaconBlockBuf:    0,
-		BeaconDB:          beaconDB,
-		DepositCache:      depositCache,
-		ChainStartFetcher: web3Service,
-		P2p:               &mockBroadcaster{},
-		StateNotifier:     &mockBeaconNode{},
-		AttPool:           attestations.NewPool(),
-		StateGen:          stategen.New(beaconDB),
-		ForkChoiceStore:   protoarray.New(0, 0, params.BeaconConfig().ZeroHash),
-		AttService:        attService,
+	stateGen := stategen.New(beaconDB)
+	// Safe a state in stategen to purposes of testing a service stop / shutdown.
+	require.NoError(t, stateGen.SaveState(ctx, bytesutil.ToBytes32(bState.FinalizedCheckpoint().Root), bState))
+
+	opts := []Option{
+		WithDatabase(beaconDB),
+		WithDepositCache(depositCache),
+		WithChainStartFetcher(web3Service),
+		WithAttestationPool(attestations.NewPool()),
+		WithP2PBroadcaster(&mockBroadcaster{}),
+		WithStateNotifier(&mockBeaconNode{}),
+		WithForkChoiceStore(protoarray.New(0, 0, params.BeaconConfig().ZeroHash)),
+		WithAttestationService(attService),
+		WithStateGen(stateGen),
 	}

-	// Safe a state in stategen to purposes of testing a service stop / shutdown.
-	require.NoError(t, cfg.StateGen.SaveState(ctx, bytesutil.ToBytes32(bState.FinalizedCheckpoint().Root), bState))
-
-	chainService, err := NewService(ctx, cfg)
+	chainService, err := NewService(ctx, opts...)
 	require.NoError(t, err, "Unable to setup chain service")
 	chainService.genesisTime = time.Unix(1, 0) // non-zero time

@@ -140,7 +144,9 @@ func TestChainStartStop_Initialized(t *testing.T) {
 	genesisBlk := util.NewBeaconBlock()
 	blkRoot, err := genesisBlk.Block.HashTreeRoot()
 	require.NoError(t, err)
-	require.NoError(t, beaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(genesisBlk)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(genesisBlk)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))
 	s, err := util.NewBeaconState()
 	require.NoError(t, err)
 	require.NoError(t, s.SetSlot(1))
@@ -149,7 +155,12 @@ func TestChainStartStop_Initialized(t *testing.T) {
 	require.NoError(t, beaconDB.SaveGenesisBlockRoot(ctx, blkRoot))
 	require.NoError(t, beaconDB.SaveJustifiedCheckpoint(ctx, &ethpb.Checkpoint{Root: blkRoot[:]}))
 	require.NoError(t, beaconDB.SaveFinalizedCheckpoint(ctx, &ethpb.Checkpoint{Root: blkRoot[:]}))
-
+	ss := &ethpb.StateSummary{
+		Slot: 1,
+		Root: blkRoot[:],
+	}
+	require.NoError(t, beaconDB.SaveStateSummary(ctx, ss))
+	chainService.cfg.FinalizedStateAtStartUp = s
 	// Test the start function.
 	chainService.Start()

@@ -170,13 +181,17 @@ func TestChainStartStop_GenesisZeroHashes(t *testing.T) {
 	genesisBlk := util.NewBeaconBlock()
 	blkRoot, err := genesisBlk.Block.HashTreeRoot()
 	require.NoError(t, err)
-	require.NoError(t, beaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(genesisBlk)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(genesisBlk)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))
 	s, err := util.NewBeaconState()
 	require.NoError(t, err)
 	require.NoError(t, beaconDB.SaveState(ctx, s, blkRoot))
 	require.NoError(t, beaconDB.SaveGenesisBlockRoot(ctx, blkRoot))
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))
 	require.NoError(t, beaconDB.SaveJustifiedCheckpoint(ctx, &ethpb.Checkpoint{Root: params.BeaconConfig().ZeroHash[:]}))
-
+	require.NoError(t, beaconDB.SaveFinalizedCheckpoint(ctx, &ethpb.Checkpoint{Root: blkRoot[:]}))
+	chainService.cfg.FinalizedStateAtStartUp = s
 	// Test the start function.
 	chainService.Start()

@@ -239,7 +254,9 @@ func TestChainService_CorrectGenesisRoots(t *testing.T) {
 	genesisBlk := util.NewBeaconBlock()
 	blkRoot, err := genesisBlk.Block.HashTreeRoot()
 	require.NoError(t, err)
-	require.NoError(t, beaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(genesisBlk)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(genesisBlk)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))
 	s, err := util.NewBeaconState()
 	require.NoError(t, err)
 	require.NoError(t, s.SetSlot(0))
@@ -247,12 +264,12 @@ func TestChainService_CorrectGenesisRoots(t *testing.T) {
 	require.NoError(t, beaconDB.SaveHeadBlockRoot(ctx, blkRoot))
 	require.NoError(t, beaconDB.SaveGenesisBlockRoot(ctx, blkRoot))
 	require.NoError(t, beaconDB.SaveFinalizedCheckpoint(ctx, &ethpb.Checkpoint{Root: blkRoot[:]}))
-
+	chainService.cfg.FinalizedStateAtStartUp = s
 	// Test the start function.
 	chainService.Start()

-	require.DeepEqual(t, blkRoot[:], chainService.finalizedCheckpt.Root, "Finalize Checkpoint root is incorrect")
-	require.DeepEqual(t, params.BeaconConfig().ZeroHash[:], chainService.justifiedCheckpt.Root, "Justified Checkpoint root is incorrect")
+	require.DeepEqual(t, blkRoot[:], chainService.store.FinalizedCheckpt().Root, "Finalize Checkpoint root is incorrect")
+	require.DeepEqual(t, params.BeaconConfig().ZeroHash[:], chainService.store.JustifiedCheckpt().Root, "Justified Checkpoint root is incorrect")

 	require.NoError(t, chainService.Stop(), "Unable to stop chain service")

@@ -266,7 +283,9 @@ func TestChainService_InitializeChainInfo(t *testing.T) {
 	genesisRoot, err := genesis.Block.HashTreeRoot()
 	require.NoError(t, err)
 	require.NoError(t, beaconDB.SaveGenesisBlockRoot(ctx, genesisRoot))
-	require.NoError(t, beaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(genesis)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(genesis)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))

 	finalizedSlot := params.BeaconConfig().SlotsPerEpoch*2 + 1
 	headBlock := util.NewBeaconBlock()
@@ -275,15 +294,22 @@ func TestChainService_InitializeChainInfo(t *testing.T) {
 	headState, err := util.NewBeaconState()
 	require.NoError(t, err)
 	require.NoError(t, headState.SetSlot(finalizedSlot))
-	require.NoError(t, headState.SetGenesisValidatorRoot(params.BeaconConfig().ZeroHash[:]))
+	require.NoError(t, headState.SetGenesisValidatorsRoot(params.BeaconConfig().ZeroHash[:]))
 	headRoot, err := headBlock.Block.HashTreeRoot()
 	require.NoError(t, err)
 	require.NoError(t, beaconDB.SaveState(ctx, headState, headRoot))
 	require.NoError(t, beaconDB.SaveState(ctx, headState, genesisRoot))
-	require.NoError(t, beaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(headBlock)))
+	wsb, err = wrapper.WrappedSignedBeaconBlock(headBlock)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))
 	require.NoError(t, beaconDB.SaveFinalizedCheckpoint(ctx, &ethpb.Checkpoint{Epoch: slots.ToEpoch(finalizedSlot), Root: headRoot[:]}))
-	c := &Service{cfg: &Config{BeaconDB: beaconDB, StateGen: stategen.New(beaconDB)}}
-	require.NoError(t, c.initializeChainInfo(ctx))
+	attSrv, err := attestations.NewService(ctx, &attestations.Config{})
+	require.NoError(t, err)
+	stateGen := stategen.New(beaconDB)
+	c, err := NewService(ctx, WithDatabase(beaconDB), WithStateGen(stateGen), WithAttestationService(attSrv), WithStateNotifier(&mock.MockStateNotifier{}), WithFinalizedStateAtStartUp(headState))
+	require.NoError(t, err)
+	require.NoError(t, stateGen.SaveState(ctx, headRoot, headState))
+	require.NoError(t, c.StartFromSavedState(headState))
 	headBlk, err := c.HeadBlock(ctx)
 	require.NoError(t, err)
 	assert.DeepEqual(t, headBlock, headBlk.Proto(), "Head block incorrect")
@@ -296,7 +322,7 @@ func TestChainService_InitializeChainInfo(t *testing.T) {
 	if !bytes.Equal(headRoot[:], r) {
 		t.Error("head slot incorrect")
 	}
-	assert.Equal(t, genesisRoot, c.genesisRoot, "Genesis block root incorrect")
+	assert.Equal(t, genesisRoot, c.originBlockRoot, "Genesis block root incorrect")
 }

 func TestChainService_InitializeChainInfo_SetHeadAtGenesis(t *testing.T) {
@@ -307,7 +333,9 @@ func TestChainService_InitializeChainInfo_SetHeadAtGenesis(t *testing.T) {
 	genesisRoot, err := genesis.Block.HashTreeRoot()
 	require.NoError(t, err)
 	require.NoError(t, beaconDB.SaveGenesisBlockRoot(ctx, genesisRoot))
-	require.NoError(t, beaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(genesis)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(genesis)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))

 	finalizedSlot := params.BeaconConfig().SlotsPerEpoch*2 + 1
 	headBlock := util.NewBeaconBlock()
@@ -316,19 +344,32 @@ func TestChainService_InitializeChainInfo_SetHeadAtGenesis(t *testing.T) {
 	headState, err := util.NewBeaconState()
 	require.NoError(t, err)
 	require.NoError(t, headState.SetSlot(finalizedSlot))
-	require.NoError(t, headState.SetGenesisValidatorRoot(params.BeaconConfig().ZeroHash[:]))
+	require.NoError(t, headState.SetGenesisValidatorsRoot(params.BeaconConfig().ZeroHash[:]))
 	headRoot, err := headBlock.Block.HashTreeRoot()
 	require.NoError(t, err)
 	require.NoError(t, beaconDB.SaveState(ctx, headState, headRoot))
 	require.NoError(t, beaconDB.SaveState(ctx, headState, genesisRoot))
-	require.NoError(t, beaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(headBlock)))
-	c := &Service{cfg: &Config{BeaconDB: beaconDB, StateGen: stategen.New(beaconDB)}}
-	require.NoError(t, c.initializeChainInfo(ctx))
+	wsb, err = wrapper.WrappedSignedBeaconBlock(headBlock)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))
+	attSrv, err := attestations.NewService(ctx, &attestations.Config{})
+	require.NoError(t, err)
+	ss := &ethpb.StateSummary{
+		Slot: finalizedSlot,
+		Root: headRoot[:],
+	}
+	require.NoError(t, beaconDB.SaveStateSummary(ctx, ss))
+	require.NoError(t, beaconDB.SaveFinalizedCheckpoint(ctx, &ethpb.Checkpoint{Root: headRoot[:], Epoch: slots.ToEpoch(finalizedSlot)}))
+	stateGen := stategen.New(beaconDB)
+	c, err := NewService(ctx, WithDatabase(beaconDB), WithStateGen(stateGen), WithAttestationService(attSrv), WithStateNotifier(&mock.MockStateNotifier{}), WithFinalizedStateAtStartUp(headState))
+	require.NoError(t, err)
+
+	require.NoError(t, c.StartFromSavedState(headState))
 	s, err := c.HeadState(ctx)
 	require.NoError(t, err)
 	assert.DeepSSZEqual(t, headState.InnerStateUnsafe(), s.InnerStateUnsafe(), "Head state incorrect")
-	assert.Equal(t, genesisRoot, c.genesisRoot, "Genesis block root incorrect")
-	assert.DeepEqual(t, genesis, c.head.block.Proto())
+	assert.Equal(t, genesisRoot, c.originBlockRoot, "Genesis block root incorrect")
+	assert.DeepEqual(t, headBlock, c.head.block.Proto())
 }

 func TestChainService_InitializeChainInfo_HeadSync(t *testing.T) {
@@ -349,14 +390,18 @@ func TestChainService_InitializeChainInfo_HeadSync(t *testing.T) {
 	genesisRoot, err := genesisBlock.Block.HashTreeRoot()
 	require.NoError(t, err)
 	require.NoError(t, beaconDB.SaveGenesisBlockRoot(ctx, genesisRoot))
-	require.NoError(t, beaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(genesisBlock)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(genesisBlock)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))

 	finalizedBlock := util.NewBeaconBlock()
 	finalizedBlock.Block.Slot = finalizedSlot
 	finalizedBlock.Block.ParentRoot = genesisRoot[:]
 	finalizedRoot, err := finalizedBlock.Block.HashTreeRoot()
 	require.NoError(t, err)
-	require.NoError(t, beaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(finalizedBlock)))
+	wsb, err = wrapper.WrappedSignedBeaconBlock(finalizedBlock)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))

 	// Set head slot close to the finalization point, no head sync is triggered.
 	headBlock := util.NewBeaconBlock()
@@ -364,28 +409,32 @@ func TestChainService_InitializeChainInfo_HeadSync(t *testing.T) {
 	headBlock.Block.ParentRoot = finalizedRoot[:]
 	headRoot, err := headBlock.Block.HashTreeRoot()
 	require.NoError(t, err)
-	require.NoError(t, beaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(headBlock)))
+	wsb, err = wrapper.WrappedSignedBeaconBlock(headBlock)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))

 	headState, err := util.NewBeaconState()
 	require.NoError(t, err)
 	require.NoError(t, headState.SetSlot(headBlock.Block.Slot))
-	require.NoError(t, headState.SetGenesisValidatorRoot(params.BeaconConfig().ZeroHash[:]))
-	require.NoError(t, beaconDB.SaveState(ctx, headState, genesisRoot))
-	require.NoError(t, beaconDB.SaveState(ctx, headState, finalizedRoot))
+	require.NoError(t, headState.SetGenesisValidatorsRoot(params.BeaconConfig().ZeroHash[:]))
 	require.NoError(t, beaconDB.SaveState(ctx, headState, headRoot))
+	require.NoError(t, beaconDB.SaveState(ctx, headState, finalizedRoot))
 	require.NoError(t, beaconDB.SaveHeadBlockRoot(ctx, headRoot))
 	require.NoError(t, beaconDB.SaveFinalizedCheckpoint(ctx, &ethpb.Checkpoint{
 		Epoch: slots.ToEpoch(finalizedBlock.Block.Slot),
 		Root:  finalizedRoot[:],
 	}))

-	c := &Service{cfg: &Config{BeaconDB: beaconDB, StateGen: stategen.New(beaconDB)}}
-
-	require.NoError(t, c.initializeChainInfo(ctx))
+	attSrv, err := attestations.NewService(ctx, &attestations.Config{})
+	require.NoError(t, err)
+	stateGen := stategen.New(beaconDB)
+	c, err := NewService(ctx, WithDatabase(beaconDB), WithStateGen(stateGen), WithAttestationService(attSrv), WithStateNotifier(&mock.MockStateNotifier{}), WithFinalizedStateAtStartUp(headState))
+	require.NoError(t, err)
+	require.NoError(t, c.StartFromSavedState(headState))
 	s, err := c.HeadState(ctx)
 	require.NoError(t, err)
 	assert.DeepSSZEqual(t, headState.InnerStateUnsafe(), s.InnerStateUnsafe(), "Head state incorrect")
-	assert.Equal(t, genesisRoot, c.genesisRoot, "Genesis block root incorrect")
+	assert.Equal(t, genesisRoot, c.originBlockRoot, "Genesis block root incorrect")
 	// Since head sync is not triggered, chain is initialized to the last finalization checkpoint.
 	assert.DeepEqual(t, finalizedBlock, c.head.block.Proto())
 	assert.LogsContain(t, hook, "resetting head from the checkpoint ('--head-sync' flag is ignored)")
@@ -397,16 +446,18 @@ func TestChainService_InitializeChainInfo_HeadSync(t *testing.T) {
 	headBlock.Block.ParentRoot = finalizedRoot[:]
 	headRoot, err = headBlock.Block.HashTreeRoot()
 	require.NoError(t, err)
-	require.NoError(t, beaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(headBlock)))
+	wsb, err = wrapper.WrappedSignedBeaconBlock(headBlock)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(ctx, wsb))
 	require.NoError(t, beaconDB.SaveState(ctx, headState, headRoot))
 	require.NoError(t, beaconDB.SaveHeadBlockRoot(ctx, headRoot))

 	hook.Reset()
-	require.NoError(t, c.initializeChainInfo(ctx))
+	require.NoError(t, c.initializeHeadFromDB(ctx))
 	s, err = c.HeadState(ctx)
 	require.NoError(t, err)
 	assert.DeepSSZEqual(t, headState.InnerStateUnsafe(), s.InnerStateUnsafe(), "Head state incorrect")
-	assert.Equal(t, genesisRoot, c.genesisRoot, "Genesis block root incorrect")
+	assert.Equal(t, genesisRoot, c.originBlockRoot, "Genesis block root incorrect")
 	// Head slot is far beyond the latest finalized checkpoint, head sync is triggered.
 	assert.DeepEqual(t, headBlock, c.head.block.Proto())
 	assert.LogsContain(t, hook, "Regenerating state from the last checkpoint at slot 225")
@@ -417,7 +468,7 @@ func TestChainService_SaveHeadNoDB(t *testing.T) {
 	beaconDB := testDB.SetupDB(t)
 	ctx := context.Background()
 	s := &Service{
-		cfg: &Config{BeaconDB: beaconDB, StateGen: stategen.New(beaconDB)},
+		cfg: &config{BeaconDB: beaconDB, StateGen: stategen.New(beaconDB)},
 	}
 	blk := util.NewBeaconBlock()
 	blk.Block.Slot = 1
@@ -426,7 +477,9 @@ func TestChainService_SaveHeadNoDB(t *testing.T) {
 	newState, err := util.NewBeaconState()
 	require.NoError(t, err)
 	require.NoError(t, s.cfg.StateGen.SaveState(ctx, r, newState))
-	require.NoError(t, s.saveHeadNoDB(ctx, wrapper.WrappedPhase0SignedBeaconBlock(blk), r, newState))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(blk)
+	require.NoError(t, err)
+	require.NoError(t, s.saveHeadNoDB(ctx, wsb, r, newState))

 	newB, err := s.cfg.BeaconDB.HeadBlock(ctx)
 	require.NoError(t, err)
@@ -435,19 +488,43 @@ func TestChainService_SaveHeadNoDB(t *testing.T) {
 	}
 }

-func TestHasBlock_ForkChoiceAndDB(t *testing.T) {
+func TestHasBlock_ForkChoiceAndDB_ProtoArray(t *testing.T) {
 	ctx := context.Background()
 	beaconDB := testDB.SetupDB(t)
 	s := &Service{
-		cfg:              &Config{ForkChoiceStore: protoarray.New(0, 0, [32]byte{}), BeaconDB: beaconDB},
-		finalizedCheckpt: &ethpb.Checkpoint{Root: make([]byte, 32)},
+		cfg:   &config{ForkChoiceStore: protoarray.New(0, 0, [32]byte{}), BeaconDB: beaconDB},
+		store: &store.Store{},
 	}
+	s.store.SetFinalizedCheckpt(&ethpb.Checkpoint{Epoch: 0, Root: params.BeaconConfig().ZeroHash[:]})
 	block := util.NewBeaconBlock()
 	r, err := block.Block.HashTreeRoot()
 	require.NoError(t, err)
 	beaconState, err := util.NewBeaconState()
 	require.NoError(t, err)
-	require.NoError(t, s.insertBlockAndAttestationsToForkChoiceStore(ctx, wrapper.WrappedPhase0SignedBeaconBlock(block).Block(), r, beaconState))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(block)
+	require.NoError(t, err)
+	require.NoError(t, s.insertBlockAndAttestationsToForkChoiceStore(ctx, wsb.Block(), r, beaconState))
+
+	assert.Equal(t, false, s.hasBlock(ctx, [32]byte{}), "Should not have block")
+	assert.Equal(t, true, s.hasBlock(ctx, r), "Should have block")
+}
+
+func TestHasBlock_ForkChoiceAndDB_DoublyLinkedTree(t *testing.T) {
+	ctx := context.Background()
+	beaconDB := testDB.SetupDB(t)
+	s := &Service{
+		cfg:   &config{ForkChoiceStore: doublylinkedtree.New(0, 0), BeaconDB: beaconDB},
+		store: &store.Store{},
+	}
+	s.store.SetFinalizedCheckpt(&ethpb.Checkpoint{Epoch: 0, Root: params.BeaconConfig().ZeroHash[:]})
+	block := util.NewBeaconBlock()
+	r, err := block.Block.HashTreeRoot()
+	require.NoError(t, err)
+	beaconState, err := util.NewBeaconState()
+	require.NoError(t, err)
+	wsb, err := wrapper.WrappedSignedBeaconBlock(block)
+	require.NoError(t, err)
+	require.NoError(t, s.insertBlockAndAttestationsToForkChoiceStore(ctx, wsb.Block(), r, beaconState))

 	assert.Equal(t, false, s.hasBlock(ctx, [32]byte{}), "Should not have block")
 	assert.Equal(t, true, s.hasBlock(ctx, r), "Should have block")
@@ -457,7 +534,7 @@ func TestServiceStop_SaveCachedBlocks(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 	beaconDB := testDB.SetupDB(t)
 	s := &Service{
-		cfg:            &Config{BeaconDB: beaconDB, StateGen: stategen.New(beaconDB)},
+		cfg:            &config{BeaconDB: beaconDB, StateGen: stategen.New(beaconDB)},
 		ctx:            ctx,
 		cancel:         cancel,
 		initSyncBlocks: make(map[[32]byte]block.SignedBeaconBlock),
@@ -465,7 +542,9 @@ func TestServiceStop_SaveCachedBlocks(t *testing.T) {
 	block := util.NewBeaconBlock()
 	r, err := block.Block.HashTreeRoot()
 	require.NoError(t, err)
-	s.saveInitSyncBlock(r, wrapper.WrappedPhase0SignedBeaconBlock(block))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(block)
+	require.NoError(t, err)
+	s.saveInitSyncBlock(r, wsb)
 	require.NoError(t, s.Stop())
 	require.Equal(t, true, s.cfg.BeaconDB.HasBlock(ctx, r))
 }
@@ -476,7 +555,7 @@ func TestProcessChainStartTime_ReceivedFeed(t *testing.T) {
 	stateChannel := make(chan *feed.Event, 1)
 	stateSub := service.cfg.StateNotifier.StateFeed().Subscribe(stateChannel)
 	defer stateSub.Unsubscribe()
-	service.processChainStartTime(context.Background(), time.Now())
+	service.onPowchainStart(context.Background(), time.Now())

 	stateEvent := <-stateChannel
 	require.Equal(t, int(stateEvent.Type), statefeed.Initialized)
@@ -488,10 +567,12 @@ func BenchmarkHasBlockDB(b *testing.B) {
 	beaconDB := testDB.SetupDB(b)
 	ctx := context.Background()
 	s := &Service{
-		cfg: &Config{BeaconDB: beaconDB},
+		cfg: &config{BeaconDB: beaconDB},
 	}
 	block := util.NewBeaconBlock()
-	require.NoError(b, s.cfg.BeaconDB.SaveBlock(ctx, wrapper.WrappedPhase0SignedBeaconBlock(block)))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(block)
+	require.NoError(b, err)
+	require.NoError(b, s.cfg.BeaconDB.SaveBlock(ctx, wsb))
 	r, err := block.Block.HashTreeRoot()
 	require.NoError(b, err)

@@ -501,20 +582,46 @@ func BenchmarkHasBlockDB(b *testing.B) {
 	}
 }

-func BenchmarkHasBlockForkChoiceStore(b *testing.B) {
+func BenchmarkHasBlockForkChoiceStore_ProtoArray(b *testing.B) {
 	ctx := context.Background()
 	beaconDB := testDB.SetupDB(b)
 	s := &Service{
-		cfg:              &Config{ForkChoiceStore: protoarray.New(0, 0, [32]byte{}), BeaconDB: beaconDB},
-		finalizedCheckpt: &ethpb.Checkpoint{Root: make([]byte, 32)},
+		cfg:   &config{ForkChoiceStore: protoarray.New(0, 0, [32]byte{}), BeaconDB: beaconDB},
+		store: &store.Store{},
 	}
-	block := &ethpb.SignedBeaconBlock{Block: &ethpb.BeaconBlock{Body: &ethpb.BeaconBlockBody{}}}
-	r, err := block.Block.HashTreeRoot()
+	s.store.SetFinalizedCheckpt(&ethpb.Checkpoint{Epoch: 0, Root: params.BeaconConfig().ZeroHash[:]})
+	blk := &ethpb.SignedBeaconBlock{Block: &ethpb.BeaconBlock{Body: &ethpb.BeaconBlockBody{}}}
+	r, err := blk.Block.HashTreeRoot()
 	require.NoError(b, err)
 	bs := &ethpb.BeaconState{FinalizedCheckpoint: &ethpb.Checkpoint{Root: make([]byte, 32)}, CurrentJustifiedCheckpoint: &ethpb.Checkpoint{Root: make([]byte, 32)}}
 	beaconState, err := v1.InitializeFromProto(bs)
 	require.NoError(b, err)
-	require.NoError(b, s.insertBlockAndAttestationsToForkChoiceStore(ctx, wrapper.WrappedPhase0SignedBeaconBlock(block).Block(), r, beaconState))
+	wsb, err := wrapper.WrappedSignedBeaconBlock(blk)
+	require.NoError(b, err)
+	require.NoError(b, s.insertBlockAndAttestationsToForkChoiceStore(ctx, wsb.Block(), r, beaconState))
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		require.Equal(b, true, s.cfg.ForkChoiceStore.HasNode(r), "Block is not in fork choice store")
+	}
+}
+func BenchmarkHasBlockForkChoiceStore_DoublyLinkedTree(b *testing.B) {
+	ctx := context.Background()
+	beaconDB := testDB.SetupDB(b)
+	s := &Service{
+		cfg:   &config{ForkChoiceStore: doublylinkedtree.New(0, 0), BeaconDB: beaconDB},
+		store: &store.Store{},
+	}
+	s.store.SetFinalizedCheckpt(&ethpb.Checkpoint{Epoch: 0, Root: params.BeaconConfig().ZeroHash[:]})
+	block := &ethpb.SignedBeaconBlock{Block: &ethpb.BeaconBlock{Body: &ethpb.BeaconBlockBody{}}}
+	r, err := block.Block.HashTreeRoot()
+	require.NoError(b, err)
+	bs := &ethpb.BeaconState{FinalizedCheckpoint: &ethpb.Checkpoint{Root: make([]byte, 32)}, CurrentJustifiedCheckpoint: &ethpb.Checkpoint{Root: make([]byte, 32)}}
+	beaconState, err := v1.InitializeFromProto(bs)
+	require.NoError(b, err)
+	wsb, err := wrapper.WrappedSignedBeaconBlock(block)
+	require.NoError(b, err)
+	require.NoError(b, s.insertBlockAndAttestationsToForkChoiceStore(ctx, wsb.Block(), r, beaconState))

 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
--- a/beacon-chain/blockchain/state_balance_cache.go
+++ b/beacon-chain/blockchain/state_balance_cache.go
@@ -0,0 +1,83 @@
+package blockchain
+
+import (
+	"context"
+	"errors"
+	"sync"
+
+	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
+	"github.com/prysmaticlabs/prysm/beacon-chain/core/time"
+	"github.com/prysmaticlabs/prysm/beacon-chain/state"
+	"github.com/prysmaticlabs/prysm/beacon-chain/state/stategen"
+)
+
+var errNilStateFromStategen = errors.New("justified state can't be nil")
+
+type stateBalanceCache struct {
+	sync.Mutex
+	balances []uint64
+	root     [32]byte
+	stateGen stateByRooter
+}
+
+type stateByRooter interface {
+	StateByRoot(context.Context, [32]byte) (state.BeaconState, error)
+}
+
+// newStateBalanceCache exists to remind us that stateBalanceCache needs a stagegen
+// to avoid nil pointer bugs when updating the cache in the read path (get())
+func newStateBalanceCache(sg *stategen.State) (*stateBalanceCache, error) {
+	if sg == nil {
+		return nil, errors.New("can't initialize state balance cache without stategen")
+	}
+	return &stateBalanceCache{stateGen: sg}, nil
+}
+
+// update is called by get() when the requested root doesn't match
+// the previously read value. This cache assumes we only want to cache one
+// set of balances for a single root (the current justified root).
+//
+// warning: this is not thread-safe on its own, relies on get() for locking
+func (c *stateBalanceCache) update(ctx context.Context, justifiedRoot [32]byte) ([]uint64, error) {
+	stateBalanceCacheMiss.Inc()
+	justifiedState, err := c.stateGen.StateByRoot(ctx, justifiedRoot)
+	if err != nil {
+		return nil, err
+	}
+	if justifiedState == nil || justifiedState.IsNil() {
+		return nil, errNilStateFromStategen
+	}
+	epoch := time.CurrentEpoch(justifiedState)
+
+	justifiedBalances := make([]uint64, justifiedState.NumValidators())
+	var balanceAccumulator = func(idx int, val state.ReadOnlyValidator) error {
+		if helpers.IsActiveValidatorUsingTrie(val, epoch) {
+			justifiedBalances[idx] = val.EffectiveBalance()
+		} else {
+			justifiedBalances[idx] = 0
+		}
+		return nil
+	}
+	if err := justifiedState.ReadFromEveryValidator(balanceAccumulator); err != nil {
+		return nil, err
+	}
+
+	c.balances = justifiedBalances
+	c.root = justifiedRoot
+	return c.balances, nil
+}
+
+// getBalances takes an explicit justifiedRoot so it can invalidate the singleton cache key
+// when the justified root changes, and takes a context so that the long-running stategen
+// read path can connect to the upstream cancellation/timeout chain.
+func (c *stateBalanceCache) get(ctx context.Context, justifiedRoot [32]byte) ([]uint64, error) {
+	c.Lock()
+	defer c.Unlock()
+
+	if justifiedRoot != [32]byte{} && justifiedRoot == c.root {
+		stateBalanceCacheHit.Inc()
+		return c.balances, nil
+	}
+
+	return c.update(ctx, justifiedRoot)
+}
--- a/beacon-chain/blockchain/state_balance_cache_test.go
+++ b/beacon-chain/blockchain/state_balance_cache_test.go
@@ -0,0 +1,236 @@
+package blockchain
+
+import (
+	"context"
+	"encoding/binary"
+	"errors"
+	"testing"
+
+	types "github.com/prysmaticlabs/eth2-types"
+	"github.com/prysmaticlabs/prysm/beacon-chain/state"
+	v2 "github.com/prysmaticlabs/prysm/beacon-chain/state/v2"
+	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
+	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
+	"github.com/prysmaticlabs/prysm/testing/require"
+	"github.com/prysmaticlabs/prysm/time/slots"
+)
+
+type mockStateByRoot struct {
+	state state.BeaconState
+	err   error
+}
+
+func (m *mockStateByRoot) StateByRoot(context.Context, [32]byte) (state.BeaconState, error) {
+	return m.state, m.err
+}
+
+type testStateOpt func(*ethpb.BeaconStateAltair)
+
+func testStateWithValidators(v []*ethpb.Validator) testStateOpt {
+	return func(a *ethpb.BeaconStateAltair) {
+		a.Validators = v
+	}
+}
+
+func testStateWithSlot(slot types.Slot) testStateOpt {
+	return func(a *ethpb.BeaconStateAltair) {
+		a.Slot = slot
+	}
+}
+
+func testStateFixture(opts ...testStateOpt) state.BeaconState {
+	a := &ethpb.BeaconStateAltair{}
+	for _, o := range opts {
+		o(a)
+	}
+	s, _ := v2.InitializeFromProtoUnsafe(a)
+	return s
+}
+
+func generateTestValidators(count int, opts ...func(*ethpb.Validator)) []*ethpb.Validator {
+	vs := make([]*ethpb.Validator, count)
+	var i uint32 = 0
+	for ; i < uint32(count); i++ {
+		pk := make([]byte, 48)
+		binary.LittleEndian.PutUint32(pk, i)
+		v := &ethpb.Validator{PublicKey: pk}
+		for _, o := range opts {
+			o(v)
+		}
+		vs[i] = v
+	}
+	return vs
+}
+
+func oddValidatorsExpired(currentSlot types.Slot) func(*ethpb.Validator) {
+	return func(v *ethpb.Validator) {
+		pki := binary.LittleEndian.Uint64(v.PublicKey)
+		if pki%2 == 0 {
+			v.ExitEpoch = types.Epoch(int(slots.ToEpoch(currentSlot)) + 1)
+		} else {
+			v.ExitEpoch = types.Epoch(int(slots.ToEpoch(currentSlot)) - 1)
+		}
+	}
+}
+
+func oddValidatorsQueued(currentSlot types.Slot) func(*ethpb.Validator) {
+	return func(v *ethpb.Validator) {
+		v.ExitEpoch = types.Epoch(int(slots.ToEpoch(currentSlot)) + 1)
+		pki := binary.LittleEndian.Uint64(v.PublicKey)
+		if pki%2 == 0 {
+			v.ActivationEpoch = types.Epoch(int(slots.ToEpoch(currentSlot)) - 1)
+		} else {
+			v.ActivationEpoch = types.Epoch(int(slots.ToEpoch(currentSlot)) + 1)
+		}
+	}
+}
+
+func allValidatorsValid(currentSlot types.Slot) func(*ethpb.Validator) {
+	return func(v *ethpb.Validator) {
+		v.ActivationEpoch = types.Epoch(int(slots.ToEpoch(currentSlot)) - 1)
+		v.ExitEpoch = types.Epoch(int(slots.ToEpoch(currentSlot)) + 1)
+	}
+}
+
+func balanceIsKeyTimes2(v *ethpb.Validator) {
+	pki := binary.LittleEndian.Uint64(v.PublicKey)
+	v.EffectiveBalance = uint64(pki) * 2
+}
+
+func testHalfExpiredValidators() ([]*ethpb.Validator, []uint64) {
+	balances := []uint64{0, 0, 4, 0, 8, 0, 12, 0, 16, 0}
+	return generateTestValidators(10,
+		oddValidatorsExpired(types.Slot(99)),
+		balanceIsKeyTimes2), balances
+}
+
+func testHalfQueuedValidators() ([]*ethpb.Validator, []uint64) {
+	balances := []uint64{0, 0, 4, 0, 8, 0, 12, 0, 16, 0}
+	return generateTestValidators(10,
+		oddValidatorsQueued(types.Slot(99)),
+		balanceIsKeyTimes2), balances
+}
+
+func testAllValidValidators() ([]*ethpb.Validator, []uint64) {
+	balances := []uint64{0, 2, 4, 6, 8, 10, 12, 14, 16, 18}
+	return generateTestValidators(10,
+		allValidatorsValid(types.Slot(99)),
+		balanceIsKeyTimes2), balances
+}
+
+func TestStateBalanceCache(t *testing.T) {
+	type sbcTestCase struct {
+		err      error
+		root     [32]byte
+		sbc      *stateBalanceCache
+		balances []uint64
+		name     string
+	}
+	sentinelCacheMiss := errors.New("Cache missed, as expected!")
+	sentinelBalances := []uint64{1, 2, 3, 4, 5}
+	halfExpiredValidators, halfExpiredBalances := testHalfExpiredValidators()
+	halfQueuedValidators, halfQueuedBalances := testHalfQueuedValidators()
+	allValidValidators, allValidBalances := testAllValidValidators()
+	cases := []sbcTestCase{
+		{
+			root:     bytesutil.ToBytes32([]byte{'A'}),
+			balances: sentinelBalances,
+			sbc: &stateBalanceCache{
+				stateGen: &mockStateByRooter{
+					err: sentinelCacheMiss,
+				},
+				root:     bytesutil.ToBytes32([]byte{'A'}),
+				balances: sentinelBalances,
+			},
+			name: "cache hit",
+		},
+		// this works by using a staterooter that returns a known error
+		// so really we're testing the miss by making sure stategen got called
+		// this also tells us stategen errors are propagated
+		{
+			sbc: &stateBalanceCache{
+				stateGen: &mockStateByRooter{
+					err: sentinelCacheMiss,
+				},
+				root: bytesutil.ToBytes32([]byte{'B'}),
+			},
+			err:  sentinelCacheMiss,
+			root: bytesutil.ToBytes32([]byte{'A'}),
+			name: "cache miss",
+		},
+		{
+			sbc: &stateBalanceCache{
+				stateGen: &mockStateByRooter{},
+				root:     bytesutil.ToBytes32([]byte{'B'}),
+			},
+			err:  errNilStateFromStategen,
+			root: bytesutil.ToBytes32([]byte{'A'}),
+			name: "error for nil state upon cache miss",
+		},
+		{
+			sbc: &stateBalanceCache{
+				stateGen: &mockStateByRooter{
+					state: testStateFixture(
+						testStateWithSlot(99),
+						testStateWithValidators(halfExpiredValidators)),
+				},
+			},
+			balances: halfExpiredBalances,
+			root:     bytesutil.ToBytes32([]byte{'A'}),
+			name:     "test filtering by exit epoch",
+		},
+		{
+			sbc: &stateBalanceCache{
+				stateGen: &mockStateByRooter{
+					state: testStateFixture(
+						testStateWithSlot(99),
+						testStateWithValidators(halfQueuedValidators)),
+				},
+			},
+			balances: halfQueuedBalances,
+			root:     bytesutil.ToBytes32([]byte{'A'}),
+			name:     "test filtering by activation epoch",
+		},
+		{
+			sbc: &stateBalanceCache{
+				stateGen: &mockStateByRooter{
+					state: testStateFixture(
+						testStateWithSlot(99),
+						testStateWithValidators(allValidValidators)),
+				},
+			},
+			balances: allValidBalances,
+			root:     bytesutil.ToBytes32([]byte{'A'}),
+			name:     "happy path",
+		},
+		{
+			sbc: &stateBalanceCache{
+				stateGen: &mockStateByRooter{
+					state: testStateFixture(
+						testStateWithSlot(99),
+						testStateWithValidators(allValidValidators)),
+				},
+			},
+			balances: allValidBalances,
+			root:     [32]byte{},
+			name:     "zero root",
+		},
+	}
+	ctx := context.Background()
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			cache := c.sbc
+			cacheRootStart := cache.root
+			b, err := cache.get(ctx, c.root)
+			require.ErrorIs(t, err, c.err)
+			require.DeepEqual(t, c.balances, b)
+			if c.err != nil {
+				// if there was an error somewhere, the root should not have changed (unless it already matched)
+				require.Equal(t, cacheRootStart, cache.root)
+			} else {
+				// when successful, the cache should always end with a root matching the request
+				require.Equal(t, c.root, cache.root)
+			}
+		})
+	}
+}
--- a/beacon-chain/blockchain/store/BUILD.bazel
+++ b/beacon-chain/blockchain/store/BUILD.bazel
@@ -0,0 +1,27 @@
+load("@prysm//tools/go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "go_default_library",
+    srcs = [
+        "doc.go",
+        "new.go",
+        "setter_getter.go",
+        "type.go",
+    ],
+    importpath = "github.com/prysmaticlabs/prysm/beacon-chain/blockchain/store",
+    visibility = ["//beacon-chain:__subpackages__"],
+    deps = ["//proto/prysm/v1alpha1:go_default_library"],
+)
+
+go_test(
+    name = "go_default_test",
+    srcs = [
+        "new_test.go",
+        "setter_getter_test.go",
+    ],
+    embed = [":go_default_library"],
+    deps = [
+        "//proto/prysm/v1alpha1:go_default_library",
+        "//testing/require:go_default_library",
+    ],
+)
--- a/beacon-chain/blockchain/store/doc.go
+++ b/beacon-chain/blockchain/store/doc.go
@@ -0,0 +1,4 @@
+// Package store implements the store object defined in the phase0 fork choice spec.
+// It serves as a helpful middleware layer in between blockchain pkg and fork choice protoarray pkg.
+// All the getters and setters are concurrent thread safe
+package store
--- a/beacon-chain/blockchain/store/new.go
+++ b/beacon-chain/blockchain/store/new.go
@@ -0,0 +1,15 @@
+package store
+
+import (
+	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
+)
+
+func New(justifiedCheckpt *ethpb.Checkpoint, finalizedCheckpt *ethpb.Checkpoint) *Store {
+	return &Store{
+		justifiedCheckpt:     justifiedCheckpt,
+		prevJustifiedCheckpt: justifiedCheckpt,
+		bestJustifiedCheckpt: justifiedCheckpt,
+		finalizedCheckpt:     finalizedCheckpt,
+		prevFinalizedCheckpt: finalizedCheckpt,
+	}
+}
--- a/beacon-chain/blockchain/store/new_test.go
+++ b/beacon-chain/blockchain/store/new_test.go
@@ -0,0 +1,25 @@
+package store
+
+import (
+	"testing"
+
+	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
+	"github.com/prysmaticlabs/prysm/testing/require"
+)
+
+func TestNew(t *testing.T) {
+	j := &ethpb.Checkpoint{
+		Epoch: 0,
+		Root:  []byte("hi"),
+	}
+	f := &ethpb.Checkpoint{
+		Epoch: 0,
+		Root:  []byte("hello"),
+	}
+	s := New(j, f)
+	require.DeepSSZEqual(t, s.JustifiedCheckpt(), j)
+	require.DeepSSZEqual(t, s.BestJustifiedCheckpt(), j)
+	require.DeepSSZEqual(t, s.PrevJustifiedCheckpt(), j)
+	require.DeepSSZEqual(t, s.FinalizedCheckpt(), f)
+	require.DeepSSZEqual(t, s.PrevFinalizedCheckpt(), f)
+}
--- a/beacon-chain/blockchain/store/setter_getter.go
+++ b/beacon-chain/blockchain/store/setter_getter.go
@@ -0,0 +1,73 @@
+package store
+
+import ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
+
+// PrevJustifiedCheckpt returns the previous justified checkpoint in the Store.
+func (s *Store) PrevJustifiedCheckpt() *ethpb.Checkpoint {
+	s.RLock()
+	defer s.RUnlock()
+	return s.prevJustifiedCheckpt
+}
+
+// BestJustifiedCheckpt returns the best justified checkpoint in the Store.
+func (s *Store) BestJustifiedCheckpt() *ethpb.Checkpoint {
+	s.RLock()
+	defer s.RUnlock()
+	return s.bestJustifiedCheckpt
+}
+
+// JustifiedCheckpt returns the justified checkpoint in the Store.
+func (s *Store) JustifiedCheckpt() *ethpb.Checkpoint {
+	s.RLock()
+	defer s.RUnlock()
+	return s.justifiedCheckpt
+}
+
+// PrevFinalizedCheckpt returns the previous finalized checkpoint in the Store.
+func (s *Store) PrevFinalizedCheckpt() *ethpb.Checkpoint {
+	s.RLock()
+	defer s.RUnlock()
+	return s.prevFinalizedCheckpt
+}
+
+// FinalizedCheckpt returns the finalized checkpoint in the Store.
+func (s *Store) FinalizedCheckpt() *ethpb.Checkpoint {
+	s.RLock()
+	defer s.RUnlock()
+	return s.finalizedCheckpt
+}
+
+// SetPrevJustifiedCheckpt sets the previous justified checkpoint in the Store.
+func (s *Store) SetPrevJustifiedCheckpt(cp *ethpb.Checkpoint) {
+	s.Lock()
+	defer s.Unlock()
+	s.prevJustifiedCheckpt = cp
+}
+
+// SetBestJustifiedCheckpt sets the best justified checkpoint in the Store.
+func (s *Store) SetBestJustifiedCheckpt(cp *ethpb.Checkpoint) {
+	s.Lock()
+	defer s.Unlock()
+	s.bestJustifiedCheckpt = cp
+}
+
+// SetJustifiedCheckpt sets the justified checkpoint in the Store.
+func (s *Store) SetJustifiedCheckpt(cp *ethpb.Checkpoint) {
+	s.Lock()
+	defer s.Unlock()
+	s.justifiedCheckpt = cp
+}
+
+// SetFinalizedCheckpt sets the finalized checkpoint in the Store.
+func (s *Store) SetFinalizedCheckpt(cp *ethpb.Checkpoint) {
+	s.Lock()
+	defer s.Unlock()
+	s.finalizedCheckpt = cp
+}
+
+// SetPrevFinalizedCheckpt sets the previous finalized checkpoint in the Store.
+func (s *Store) SetPrevFinalizedCheckpt(cp *ethpb.Checkpoint) {
+	s.Lock()
+	defer s.Unlock()
+	s.prevFinalizedCheckpt = cp
+}
--- a/beacon-chain/blockchain/store/setter_getter_test.go
+++ b/beacon-chain/blockchain/store/setter_getter_test.go
@@ -0,0 +1,53 @@
+package store
+
+import (
+	"testing"
+
+	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
+	"github.com/prysmaticlabs/prysm/testing/require"
+)
+
+func Test_store_PrevJustifiedCheckpt(t *testing.T) {
+	s := &Store{}
+	var cp *ethpb.Checkpoint
+	require.Equal(t, cp, s.PrevJustifiedCheckpt())
+	cp = &ethpb.Checkpoint{Epoch: 1, Root: []byte{'a'}}
+	s.SetPrevJustifiedCheckpt(cp)
+	require.Equal(t, cp, s.PrevJustifiedCheckpt())
+}
+
+func Test_store_BestJustifiedCheckpt(t *testing.T) {
+	s := &Store{}
+	var cp *ethpb.Checkpoint
+	require.Equal(t, cp, s.BestJustifiedCheckpt())
+	cp = &ethpb.Checkpoint{Epoch: 1, Root: []byte{'a'}}
+	s.SetBestJustifiedCheckpt(cp)
+	require.Equal(t, cp, s.BestJustifiedCheckpt())
+}
+
+func Test_store_JustifiedCheckpt(t *testing.T) {
+	s := &Store{}
+	var cp *ethpb.Checkpoint
+	require.Equal(t, cp, s.JustifiedCheckpt())
+	cp = &ethpb.Checkpoint{Epoch: 1, Root: []byte{'a'}}
+	s.SetJustifiedCheckpt(cp)
+	require.Equal(t, cp, s.JustifiedCheckpt())
+}
+
+func Test_store_FinalizedCheckpt(t *testing.T) {
+	s := &Store{}
+	var cp *ethpb.Checkpoint
+	require.Equal(t, cp, s.FinalizedCheckpt())
+	cp = &ethpb.Checkpoint{Epoch: 1, Root: []byte{'a'}}
+	s.SetFinalizedCheckpt(cp)
+	require.Equal(t, cp, s.FinalizedCheckpt())
+}
+
+func Test_store_PrevFinalizedCheckpt(t *testing.T) {
+	s := &Store{}
+	var cp *ethpb.Checkpoint
+	require.Equal(t, cp, s.PrevFinalizedCheckpt())
+	cp = &ethpb.Checkpoint{Epoch: 1, Root: []byte{'a'}}
+	s.SetPrevFinalizedCheckpt(cp)
+	require.Equal(t, cp, s.PrevFinalizedCheckpt())
+}
--- a/beacon-chain/blockchain/store/type.go
+++ b/beacon-chain/blockchain/store/type.go
@@ -0,0 +1,28 @@
+package store
+
+import (
+	"sync"
+
+	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
+)
+
+// Store is defined in the fork choice consensus spec for tracking current time and various versions of checkpoints.
+//
+// Spec code:
+// class Store(object):
+//    time: uint64
+//    genesis_time: uint64
+//    justified_checkpoint: Checkpoint
+//    finalized_checkpoint: Checkpoint
+//    best_justified_checkpoint: Checkpoint
+//    proposerBoostRoot: Root
+type Store struct {
+	justifiedCheckpt     *ethpb.Checkpoint
+	finalizedCheckpt     *ethpb.Checkpoint
+	bestJustifiedCheckpt *ethpb.Checkpoint
+	sync.RWMutex
+	// These are not part of the consensus spec, but we do use them to return gRPC API requests.
+	// TODO(10094): Consider removing in v3.
+	prevFinalizedCheckpt *ethpb.Checkpoint
+	prevJustifiedCheckpt *ethpb.Checkpoint
+}
--- a/beacon-chain/blockchain/testing/BUILD.bazel
+++ b/beacon-chain/blockchain/testing/BUILD.bazel
@@ -8,7 +8,6 @@ go_library(
    visibility = [
        "//beacon-chain:__subpackages__",
        "//testing:__subpackages__",
-        "//testing/fuzz:__pkg__",
    ],
    deps = [
        "//async/event:go_default_library",
@@ -19,9 +18,9 @@ go_library(
        "//beacon-chain/core/feed/state:go_default_library",
        "//beacon-chain/core/helpers:go_default_library",
        "//beacon-chain/db:go_default_library",
-        "//beacon-chain/forkchoice/protoarray:go_default_library",
+        "//beacon-chain/forkchoice:go_default_library",
        "//beacon-chain/state:go_default_library",
-        "//beacon-chain/state/v1:go_default_library",
+        "//config/fieldparams:go_default_library",
        "//config/params:go_default_library",
        "//encoding/bytesutil:go_default_library",
        "//proto/prysm/v1alpha1:go_default_library",
--- a/beacon-chain/blockchain/testing/mock.go
+++ b/beacon-chain/blockchain/testing/mock.go
@@ -18,9 +18,9 @@ import (
 	statefeed "github.com/prysmaticlabs/prysm/beacon-chain/core/feed/state"
 	"github.com/prysmaticlabs/prysm/beacon-chain/core/helpers"
 	"github.com/prysmaticlabs/prysm/beacon-chain/db"
-	"github.com/prysmaticlabs/prysm/beacon-chain/forkchoice/protoarray"
+	"github.com/prysmaticlabs/prysm/beacon-chain/forkchoice"
 	"github.com/prysmaticlabs/prysm/beacon-chain/state"
-	v1 "github.com/prysmaticlabs/prysm/beacon-chain/state/v1"
+	fieldparams "github.com/prysmaticlabs/prysm/config/fieldparams"
 	"github.com/prysmaticlabs/prysm/config/params"
 	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
 	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
@@ -28,36 +28,44 @@ import (
 	"github.com/sirupsen/logrus"
 )

+var ErrNilState = errors.New("nil state")
+
 // ChainService defines the mock interface for testing
 type ChainService struct {
-	State                       state.BeaconState
-	Root                        []byte
-	Block                       block.SignedBeaconBlock
+	Optimistic                  bool
+	ValidAttestation            bool
+	ValidatorsRoot              [32]byte
+	PublicKey                   [fieldparams.BLSPubkeyLength]byte
 	FinalizedCheckPoint         *ethpb.Checkpoint
 	CurrentJustifiedCheckPoint  *ethpb.Checkpoint
 	PreviousJustifiedCheckPoint *ethpb.Checkpoint
-	BlocksReceived              []block.SignedBeaconBlock
+	Slot                        *types.Slot // Pointer because 0 is a useful value, so checking against it can be incorrect.
 	Balance                     *precompute.Balance
-	Genesis                     time.Time
-	ValidatorsRoot              [32]byte
 	CanonicalRoots              map[[32]byte]bool
 	Fork                        *ethpb.Fork
 	ETH1Data                    *ethpb.Eth1Data
+	InitSyncBlockRoots          map[[32]byte]bool
 	DB                          db.Database
+	State                       state.BeaconState
+	Block                       block.SignedBeaconBlock
+	VerifyBlkDescendantErr      error
 	stateNotifier               statefeed.Notifier
+	BlocksReceived              []block.SignedBeaconBlock
+	SyncCommitteeIndices        []types.CommitteeIndex
 	blockNotifier               blockfeed.Notifier
 	opNotifier                  opfeed.Notifier
-	ValidAttestation            bool
-	ForkChoiceStore             *protoarray.Store
-	VerifyBlkDescendantErr      error
-	Slot                        *types.Slot // Pointer because 0 is a useful value, so checking against it can be incorrect.
-	SyncCommitteeIndices        []types.CommitteeIndex
+	Root                        []byte
 	SyncCommitteeDomain         []byte
 	SyncSelectionProofDomain    []byte
 	SyncContributionProofDomain []byte
-	PublicKey                   [48]byte
 	SyncCommitteePubkeys        [][]byte
-	InitSyncBlockRoots          map[[32]byte]bool
+	Genesis                     time.Time
+	ForkChoiceStore             forkchoice.ForkChoicer
+}
+
+// ForkChoicer mocks the same method in the chain service
+func (s *ChainService) ForkChoicer() forkchoice.ForkChoicer {
+	return s.ForkChoiceStore
 }

 // StateNotifier mocks the same method in the chain service.
@@ -158,7 +166,7 @@ func (mon *MockOperationNotifier) OperationFeed() *event.Feed {
 // ReceiveBlockInitialSync mocks ReceiveBlockInitialSync method in chain service.
 func (s *ChainService) ReceiveBlockInitialSync(ctx context.Context, block block.SignedBeaconBlock, _ [32]byte) error {
 	if s.State == nil {
-		s.State = &v1.BeaconState{}
+		return ErrNilState
 	}
 	if !bytes.Equal(s.Root, block.Block().ParentRoot()) {
 		return errors.Errorf("wanted %#x but got %#x", s.Root, block.Block().ParentRoot())
@@ -185,7 +193,7 @@ func (s *ChainService) ReceiveBlockInitialSync(ctx context.Context, block block.
 // ReceiveBlockBatch processes blocks in batches from initial-sync.
 func (s *ChainService) ReceiveBlockBatch(ctx context.Context, blks []block.SignedBeaconBlock, _ [][32]byte) error {
 	if s.State == nil {
-		s.State = &v1.BeaconState{}
+		return ErrNilState
 	}
 	for _, block := range blks {
 		if !bytes.Equal(s.Root, block.Block().ParentRoot()) {
@@ -214,7 +222,7 @@ func (s *ChainService) ReceiveBlockBatch(ctx context.Context, blks []block.Signe
 // ReceiveBlock mocks ReceiveBlock method in chain service.
 func (s *ChainService) ReceiveBlock(ctx context.Context, block block.SignedBeaconBlock, _ [32]byte) error {
 	if s.State == nil {
-		s.State = &v1.BeaconState{}
+		return ErrNilState
 	}
 	if !bytes.Equal(s.Root, block.Block().ParentRoot()) {
 		return errors.Errorf("wanted %#x but got %#x", s.Root, block.Block().ParentRoot())
@@ -285,12 +293,12 @@ func (s *ChainService) PreviousJustifiedCheckpt() *ethpb.Checkpoint {
 }

 // ReceiveAttestation mocks ReceiveAttestation method in chain service.
-func (s *ChainService) ReceiveAttestation(_ context.Context, _ *ethpb.Attestation) error {
+func (_ *ChainService) ReceiveAttestation(_ context.Context, _ *ethpb.Attestation) error {
 	return nil
 }

 // ReceiveAttestationNoPubsub mocks ReceiveAttestationNoPubsub method in chain service.
-func (s *ChainService) ReceiveAttestationNoPubsub(context.Context, *ethpb.Attestation) error {
+func (_ *ChainService) ReceiveAttestationNoPubsub(context.Context, *ethpb.Attestation) error {
 	return nil
 }

@@ -317,18 +325,13 @@ func (s *ChainService) HeadETH1Data() *ethpb.Eth1Data {
 	return s.ETH1Data
 }

-// ProtoArrayStore mocks the same method in the chain service.
-func (s *ChainService) ProtoArrayStore() *protoarray.Store {
-	return s.ForkChoiceStore
-}
-
 // GenesisTime mocks the same method in the chain service.
 func (s *ChainService) GenesisTime() time.Time {
 	return s.Genesis
 }

-// GenesisValidatorRoot mocks the same method in the chain service.
-func (s *ChainService) GenesisValidatorRoot() [32]byte {
+// GenesisValidatorsRoot mocks the same method in the chain service.
+func (s *ChainService) GenesisValidatorsRoot() [32]byte {
 	return s.ValidatorsRoot
 }

@@ -368,8 +371,8 @@ func (s *ChainService) HasInitSyncBlock(rt [32]byte) bool {
 	return s.InitSyncBlockRoots[rt]
 }

-// HeadGenesisValidatorRoot mocks HeadGenesisValidatorRoot method in chain service.
-func (s *ChainService) HeadGenesisValidatorRoot() [32]byte {
+// HeadGenesisValidatorsRoot mocks HeadGenesisValidatorsRoot method in chain service.
+func (_ *ChainService) HeadGenesisValidatorsRoot() [32]byte {
 	return [32]byte{}
 }

@@ -379,7 +382,7 @@ func (s *ChainService) VerifyBlkDescendant(_ context.Context, _ [32]byte) error
 }

 // VerifyLmdFfgConsistency mocks VerifyLmdFfgConsistency and always returns nil.
-func (s *ChainService) VerifyLmdFfgConsistency(_ context.Context, a *ethpb.Attestation) error {
+func (_ *ChainService) VerifyLmdFfgConsistency(_ context.Context, a *ethpb.Attestation) error {
 	if !bytes.Equal(a.Data.BeaconBlockRoot, a.Data.Target.Root) {
 		return errors.New("LMD and FFG miss matched")
 	}
@@ -395,7 +398,7 @@ func (s *ChainService) VerifyFinalizedConsistency(_ context.Context, r []byte) e
 }

 // ChainHeads mocks ChainHeads and always return nil.
-func (s *ChainService) ChainHeads() ([][32]byte, []types.Slot) {
+func (_ *ChainService) ChainHeads() ([][32]byte, []types.Slot) {
 	return [][32]byte{
 			bytesutil.ToBytes32(bytesutil.PadTo([]byte("foo"), 32)),
 			bytesutil.ToBytes32(bytesutil.PadTo([]byte("bar"), 32)),
@@ -404,12 +407,12 @@ func (s *ChainService) ChainHeads() ([][32]byte, []types.Slot) {
 }

 // HeadPublicKeyToValidatorIndex mocks HeadPublicKeyToValidatorIndex and always return 0 and true.
-func (s *ChainService) HeadPublicKeyToValidatorIndex(_ context.Context, _ [48]byte) (types.ValidatorIndex, bool) {
+func (_ *ChainService) HeadPublicKeyToValidatorIndex(_ [fieldparams.BLSPubkeyLength]byte) (types.ValidatorIndex, bool) {
 	return 0, true
 }

 // HeadValidatorIndexToPublicKey mocks HeadValidatorIndexToPublicKey and always return empty and nil.
-func (s *ChainService) HeadValidatorIndexToPublicKey(_ context.Context, _ types.ValidatorIndex) ([48]byte, error) {
+func (s *ChainService) HeadValidatorIndexToPublicKey(_ context.Context, _ types.ValidatorIndex) ([fieldparams.BLSPubkeyLength]byte, error) {
 	return s.PublicKey, nil
 }

@@ -437,3 +440,13 @@ func (s *ChainService) HeadSyncSelectionProofDomain(_ context.Context, _ types.S
 func (s *ChainService) HeadSyncContributionProofDomain(_ context.Context, _ types.Slot) ([]byte, error) {
 	return s.SyncContributionProofDomain, nil
 }
+
+// IsOptimistic mocks the same method in the chain service.
+func (s *ChainService) IsOptimistic(_ context.Context) (bool, error) {
+	return s.Optimistic, nil
+}
+
+// IsOptimisticForRoot mocks the same method in the chain service.
+func (s *ChainService) IsOptimisticForRoot(_ context.Context, _ [32]byte) (bool, error) {
+	return s.Optimistic, nil
+}
--- a/beacon-chain/blockchain/weak_subjectivity_checks.go
+++ b/beacon-chain/blockchain/weak_subjectivity_checks.go
@@ -4,57 +4,97 @@ import (
 	"context"
 	"fmt"

+	"github.com/pkg/errors"
+	types "github.com/prysmaticlabs/eth2-types"
 	"github.com/prysmaticlabs/prysm/beacon-chain/db/filters"
 	"github.com/prysmaticlabs/prysm/config/params"
 	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
+	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
 	"github.com/prysmaticlabs/prysm/time/slots"
 )

-// VerifyWeakSubjectivityRoot verifies the weak subjectivity root in the service struct.
+var errWSBlockNotFound = errors.New("weak subjectivity root not found in db")
+var errWSBlockNotFoundInEpoch = errors.New("weak subjectivity root not found in db within epoch")
+
+type weakSubjectivityDB interface {
+	HasBlock(ctx context.Context, blockRoot [32]byte) bool
+	BlockRoots(ctx context.Context, f *filters.QueryFilter) ([][32]byte, error)
+}
+
+type WeakSubjectivityVerifier struct {
+	enabled  bool
+	verified bool
+	root     [32]byte
+	epoch    types.Epoch
+	slot     types.Slot
+	db       weakSubjectivityDB
+}
+
+// NewWeakSubjectivityVerifier validates a checkpoint, and if valid, uses it to initialize a weak subjectivity verifier
+func NewWeakSubjectivityVerifier(wsc *ethpb.Checkpoint, db weakSubjectivityDB) (*WeakSubjectivityVerifier, error) {
+	// TODO(7342): Weak subjectivity checks are currently optional. When we require the flag to be specified
+	// per 7342, a nil checkpoint, zero-root or zero-epoch should all fail validation
+	// and return an error instead of creating a WeakSubjectivityVerifier that permits any chain history.
+	if wsc == nil || len(wsc.Root) == 0 || wsc.Epoch == 0 {
+		log.Warn("No valid weak subjectivity checkpoint specified, running without weak subjectivity verification")
+		return &WeakSubjectivityVerifier{
+			enabled: false,
+		}, nil
+	}
+	startSlot, err := slots.EpochStart(wsc.Epoch)
+	if err != nil {
+		return nil, err
+	}
+	return &WeakSubjectivityVerifier{
+		enabled:  true,
+		verified: false,
+		root:     bytesutil.ToBytes32(wsc.Root),
+		epoch:    wsc.Epoch,
+		db:       db,
+		slot:     startSlot,
+	}, nil
+}
+
+// VerifyWeakSubjectivity verifies the weak subjectivity root in the service struct.
 // Reference design: https://github.com/ethereum/consensus-specs/blob/master/specs/phase0/weak-subjectivity.md#weak-subjectivity-sync-procedure
-func (s *Service) VerifyWeakSubjectivityRoot(ctx context.Context) error {
-	// TODO(7342): Remove the following to fully use weak subjectivity in production.
-	if s.cfg.WeakSubjectivityCheckpt == nil || len(s.cfg.WeakSubjectivityCheckpt.Root) == 0 || s.cfg.WeakSubjectivityCheckpt.Epoch == 0 {
+func (v *WeakSubjectivityVerifier) VerifyWeakSubjectivity(ctx context.Context, finalizedEpoch types.Epoch) error {
+	if v.verified || !v.enabled {
 		return nil
 	}

-	// Do nothing if the weak subjectivity has previously been verified,
-	// or weak subjectivity epoch is higher than last finalized epoch.
-	if s.wsVerified {
-		return nil
-	}
-	if s.cfg.WeakSubjectivityCheckpt.Epoch > s.finalizedCheckpt.Epoch {
+	// Two conditions are described in the specs:
+	// IF epoch_number > store.finalized_checkpoint.epoch,
+	// then ASSERT during block sync that block with root block_root
+	// is in the sync path at epoch epoch_number. Emit descriptive critical error if this assert fails,
+	// then exit client process.
+	// we do not handle this case ^, because we can only blocks that have been processed / are currently
+	// in line for finalization, we don't have the ability to look ahead. so we only satisfy the following:
+	// IF epoch_number <= store.finalized_checkpoint.epoch,
+	// then ASSERT that the block in the canonical chain at epoch epoch_number has root block_root.
+	// Emit descriptive critical error if this assert fails, then exit client process.
+	if v.epoch > finalizedEpoch {
 		return nil
 	}
+	log.Infof("Performing weak subjectivity check for root %#x in epoch %d", v.root, v.epoch)

-	r := bytesutil.ToBytes32(s.cfg.WeakSubjectivityCheckpt.Root)
-	log.Infof("Performing weak subjectivity check for root %#x in epoch %d", r, s.cfg.WeakSubjectivityCheckpt.Epoch)
-	// Save initial sync cached blocks to DB.
-	if err := s.cfg.BeaconDB.SaveBlocks(ctx, s.getInitSyncBlocks()); err != nil {
-		return err
-	}
-	// A node should have the weak subjectivity block in the DB.
-	if !s.cfg.BeaconDB.HasBlock(ctx, r) {
-		return fmt.Errorf("node does not have root in DB: %#x", r)
-	}
-
-	startSlot, err := slots.EpochStart(s.cfg.WeakSubjectivityCheckpt.Epoch)
-	if err != nil {
-		return err
+	if !v.db.HasBlock(ctx, v.root) {
+		return errors.Wrap(errWSBlockNotFound, fmt.Sprintf("missing root %#x", v.root))
 	}
+	endSlot := v.slot + params.BeaconConfig().SlotsPerEpoch
+	filter := filters.NewFilter().SetStartSlot(v.slot).SetEndSlot(endSlot)
 	// A node should have the weak subjectivity block corresponds to the correct epoch in the DB.
-	filter := filters.NewFilter().SetStartSlot(startSlot).SetEndSlot(startSlot + params.BeaconConfig().SlotsPerEpoch)
-	roots, err := s.cfg.BeaconDB.BlockRoots(ctx, filter)
+	log.Infof("Searching block roots for weak subjectivity root=%#x, between slots %d-%d", v.root, v.slot, endSlot)
+	roots, err := v.db.BlockRoots(ctx, filter)
 	if err != nil {
-		return err
+		return errors.Wrap(err, "error while retrieving block roots to verify weak subjectivity")
 	}
 	for _, root := range roots {
-		if r == root {
-			log.Info("Weak subjectivity check has passed")
-			s.wsVerified = true
+		if v.root == root {
+			log.Info("Weak subjectivity check has passed!!")
+			v.verified = true
 			return nil
 		}
 	}

-	return fmt.Errorf("node does not have root in db corresponding to epoch: %#x %d", r, s.cfg.WeakSubjectivityCheckpt.Epoch)
+	return errors.Wrap(errWSBlockNotFoundInEpoch, fmt.Sprintf("root=%#x, epoch=%d", v.root, v.epoch))
 }
--- a/beacon-chain/blockchain/weak_subjectivity_checks_test.go
+++ b/beacon-chain/blockchain/weak_subjectivity_checks_test.go
@@ -4,78 +4,87 @@ import (
 	"context"
 	"testing"

+	"github.com/pkg/errors"
 	types "github.com/prysmaticlabs/eth2-types"
+	"github.com/prysmaticlabs/prysm/beacon-chain/blockchain/store"
 	testDB "github.com/prysmaticlabs/prysm/beacon-chain/db/testing"
+	fieldparams "github.com/prysmaticlabs/prysm/config/fieldparams"
 	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
 	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
 	"github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1/wrapper"
 	"github.com/prysmaticlabs/prysm/testing/require"
 	"github.com/prysmaticlabs/prysm/testing/util"
+	"github.com/prysmaticlabs/prysm/time/slots"
 )

 func TestService_VerifyWeakSubjectivityRoot(t *testing.T) {
 	beaconDB := testDB.SetupDB(t)

 	b := util.NewBeaconBlock()
-	b.Block.Slot = 32
-	require.NoError(t, beaconDB.SaveBlock(context.Background(), wrapper.WrappedPhase0SignedBeaconBlock(b)))
+	b.Block.Slot = 1792480
+	wsb, err := wrapper.WrappedSignedBeaconBlock(b)
+	require.NoError(t, err)
+	require.NoError(t, beaconDB.SaveBlock(context.Background(), wsb))
 	r, err := b.Block.HashTreeRoot()
 	require.NoError(t, err)
+
+	blockEpoch := slots.ToEpoch(b.Block.Slot)
 	tests := []struct {
 		wsVerified     bool
-		wantErr        bool
+		disabled       bool
+		wantErr        error
 		checkpt        *ethpb.Checkpoint
 		finalizedEpoch types.Epoch
-		errString      string
 		name           string
 	}{
 		{
-			name:    "nil root and epoch",
-			wantErr: false,
-		},
-		{
-			name:           "already verified",
-			checkpt:        &ethpb.Checkpoint{Epoch: 2},
-			finalizedEpoch: 2,
-			wsVerified:     true,
-			wantErr:        false,
+			name:     "nil root and epoch",
+			disabled: true,
 		},
 		{
 			name:           "not yet to verify, ws epoch higher than finalized epoch",
-			checkpt:        &ethpb.Checkpoint{Epoch: 2},
-			finalizedEpoch: 1,
-			wantErr:        false,
+			checkpt:        &ethpb.Checkpoint{Root: bytesutil.PadTo([]byte{'a'}, 32), Epoch: blockEpoch},
+			finalizedEpoch: blockEpoch - 1,
 		},
 		{
 			name:           "can't find the block in DB",
-			checkpt:        &ethpb.Checkpoint{Root: bytesutil.PadTo([]byte{'a'}, 32), Epoch: 1},
-			finalizedEpoch: 3,
-			wantErr:        true,
-			errString:      "node does not have root in DB",
+			checkpt:        &ethpb.Checkpoint{Root: bytesutil.PadTo([]byte{'a'}, fieldparams.RootLength), Epoch: 1},
+			finalizedEpoch: blockEpoch + 1,
+			wantErr:        errWSBlockNotFound,
 		},
 		{
 			name:           "can't find the block corresponds to ws epoch in DB",
-			checkpt:        &ethpb.Checkpoint{Root: r[:], Epoch: 2}, // Root belongs in epoch 1.
-			finalizedEpoch: 3,
-			wantErr:        true,
-			errString:      "node does not have root in db corresponding to epoch",
+			checkpt:        &ethpb.Checkpoint{Root: r[:], Epoch: blockEpoch - 2}, // Root belongs in epoch 1.
+			finalizedEpoch: blockEpoch - 1,
+			wantErr:        errWSBlockNotFoundInEpoch,
 		},
 		{
 			name:           "can verify and pass",
-			checkpt:        &ethpb.Checkpoint{Root: r[:], Epoch: 1},
-			finalizedEpoch: 3,
-			wantErr:        false,
+			checkpt:        &ethpb.Checkpoint{Root: r[:], Epoch: blockEpoch},
+			finalizedEpoch: blockEpoch + 1,
+		},
+		{
+			name:           "equal epoch",
+			checkpt:        &ethpb.Checkpoint{Root: r[:], Epoch: blockEpoch},
+			finalizedEpoch: blockEpoch,
 		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
+			wv, err := NewWeakSubjectivityVerifier(tt.checkpt, beaconDB)
+			require.Equal(t, !tt.disabled, wv.enabled)
+			require.NoError(t, err)
 			s := &Service{
-				cfg:              &Config{BeaconDB: beaconDB, WeakSubjectivityCheckpt: tt.checkpt},
-				wsVerified:       tt.wsVerified,
-				finalizedCheckpt: &ethpb.Checkpoint{Epoch: tt.finalizedEpoch},
+				cfg:        &config{BeaconDB: beaconDB, WeakSubjectivityCheckpt: tt.checkpt},
+				store:      &store.Store{},
+				wsVerifier: wv,
 			}
-			if err := s.VerifyWeakSubjectivityRoot(context.Background()); (err != nil) != tt.wantErr {
-				require.ErrorContains(t, tt.errString, err)
+			s.store.SetFinalizedCheckpt(&ethpb.Checkpoint{Epoch: tt.finalizedEpoch})
+			err = s.wsVerifier.VerifyWeakSubjectivity(context.Background(), s.store.FinalizedCheckpt().Epoch)
+			if tt.wantErr == nil {
+				require.NoError(t, err)
+			} else {
+				require.Equal(t, true, errors.Is(err, tt.wantErr))
 			}
 		})
 	}
--- a/beacon-chain/cache/BUILD.bazel
+++ b/beacon-chain/cache/BUILD.bazel
@@ -1,44 +1,35 @@
 load("@prysm//tools/go:def.bzl", "go_library", "go_test")

-# gazelle:exclude committee_disabled.go
-# gazelle:exclude proposer_indices_disabled.go
 go_library(
    name = "go_default_library",
    srcs = [
+        "active_balance.go",
+        "active_balance_disabled.go",  # keep
        "attestation_data.go",
        "checkpoint_state.go",
+        "committee.go",
+        "committee_disabled.go",  # keep
        "committees.go",
        "common.go",
        "doc.go",
        "error.go",
+        "proposer_indices.go",
+        "proposer_indices_disabled.go",  # keep
        "proposer_indices_type.go",
        "skip_slot_cache.go",
        "subnet_ids.go",
+        "sync_committee.go",
+        "sync_committee_disabled.go",  # keep
        "sync_committee_head_state.go",
        "sync_subnet_ids.go",
-    ] + select({
-        "//testing/fuzz:fuzzing_enabled": [
-            "active_balance_disabled.go",
-            "committee_disabled.go",
-            "proposer_indices_disabled.go",
-            "sync_committee_disabled.go",
-        ],
-        "//conditions:default": [
-            "active_balance.go",
-            "committee.go",
-            "proposer_indices.go",
-            "sync_committee.go",
-        ],
-    }),
+    ],
    importpath = "github.com/prysmaticlabs/prysm/beacon-chain/cache",
    visibility = [
        "//beacon-chain:__subpackages__",
-        "//testing/fuzz:__pkg__",
        "//tools:__subpackages__",
    ],
    deps = [
        "//beacon-chain/state:go_default_library",
-        "//beacon-chain/state/v2:go_default_library",
        "//cache/lru:go_default_library",
        "//config/features:go_default_library",
        "//config/params:go_default_library",
@@ -48,6 +39,7 @@ go_library(
        "//encoding/bytesutil:go_default_library",
        "//math:go_default_library",
        "//proto/prysm/v1alpha1:go_default_library",
+        "//runtime/version:go_default_library",
        "@com_github_hashicorp_golang_lru//:go_default_library",
        "@com_github_patrickmn_go_cache//:go_default_library",
        "@com_github_pkg_errors//:go_default_library",
@@ -81,7 +73,9 @@ go_test(
        "//beacon-chain/state:go_default_library",
        "//beacon-chain/state/v1:go_default_library",
        "//beacon-chain/state/v2:go_default_library",
+        "//beacon-chain/state/v3:go_default_library",
        "//config/features:go_default_library",
+        "//config/fieldparams:go_default_library",
        "//config/params:go_default_library",
        "//encoding/bytesutil:go_default_library",
        "//proto/prysm/v1alpha1:go_default_library",
--- a/beacon-chain/cache/active_balance.go
+++ b/beacon-chain/cache/active_balance.go
@@ -1,4 +1,5 @@
-// +build !libfuzzer
+//go:build !fuzz
+// +build !fuzz

 package cache

@@ -17,10 +18,12 @@ import (
 	"github.com/prysmaticlabs/prysm/config/params"
 )

-var (
+const (
 	// maxBalanceCacheSize defines the max number of active balances can cache.
-	maxBalanceCacheSize = uint64(4)
+	maxBalanceCacheSize = int(4)
+)

+var (
 	// BalanceCacheMiss tracks the number of balance requests that aren't present in the cache.
 	balanceCacheMiss = promauto.NewCounter(prometheus.CounterOpts{
 		Name: "total_effective_balance_cache_miss",
@@ -42,7 +45,7 @@ type BalanceCache struct {
 // NewEffectiveBalanceCache creates a new effective balance cache for storing/accessing total balance by epoch.
 func NewEffectiveBalanceCache() *BalanceCache {
 	return &BalanceCache{
-		cache: lruwrpr.New(int(maxBalanceCacheSize)),
+		cache: lruwrpr.New(maxBalanceCacheSize),
 	}
 }

--- a/beacon-chain/cache/active_balance_disabled.go
+++ b/beacon-chain/cache/active_balance_disabled.go
@@ -1,4 +1,5 @@
-// +build libfuzzer
+//go:build fuzz
+// +build fuzz

 package cache

--- a/beacon-chain/cache/committee.go
+++ b/beacon-chain/cache/committee.go
@@ -1,4 +1,5 @@
-// +build !libfuzzer
+//go:build !fuzz
+// +build !fuzz

 package cache

@@ -19,11 +20,13 @@ import (
 	mathutil "github.com/prysmaticlabs/prysm/math"
 )

-var (
+const (
 	// maxCommitteesCacheSize defines the max number of shuffled committees on per randao basis can cache.
 	// Due to reorgs and long finality, it's good to keep the old cache around for quickly switch over.
-	maxCommitteesCacheSize = uint64(32)
+	maxCommitteesCacheSize = int(32)
+)

+var (
 	// CommitteeCacheMiss tracks the number of committee requests that aren't present in the cache.
 	CommitteeCacheMiss = promauto.NewCounter(prometheus.CounterOpts{
 		Name: "committee_cache_miss",
@@ -55,7 +58,7 @@ func committeeKeyFn(obj interface{}) (string, error) {
 // NewCommitteesCache creates a new committee cache for storing/accessing shuffled indices of a committee.
 func NewCommitteesCache() *CommitteeCache {
 	return &CommitteeCache{
-		CommitteeCache: lruwrpr.New(int(maxCommitteesCacheSize)),
+		CommitteeCache: lruwrpr.New(maxCommitteesCacheSize),
 		inProgress:     make(map[string]bool),
 	}
 }
--- a/beacon-chain/cache/committee_disabled.go
+++ b/beacon-chain/cache/committee_disabled.go
@@ -1,4 +1,5 @@
-// +build libfuzzer
+//go:build fuzz
+// +build fuzz

 // This file is used in fuzzer builds to bypass global committee caches.
 package cache
--- a/beacon-chain/cache/committee_fuzz_test.go
+++ b/beacon-chain/cache/committee_fuzz_test.go
@@ -33,7 +33,7 @@ func TestCommitteeCache_FuzzCommitteesByEpoch(t *testing.T) {
 		require.NoError(t, err)
 	}

-	assert.Equal(t, maxCommitteesCacheSize, uint64(len(cache.CommitteeCache.Keys())), "Incorrect key size")
+	assert.Equal(t, maxCommitteesCacheSize, len(cache.CommitteeCache.Keys()), "Incorrect key size")
 }

 func TestCommitteeCache_FuzzActiveIndices(t *testing.T) {
@@ -50,5 +50,5 @@ func TestCommitteeCache_FuzzActiveIndices(t *testing.T) {
 		assert.DeepEqual(t, c.SortedIndices, indices)
 	}

-	assert.Equal(t, maxCommitteesCacheSize, uint64(len(cache.CommitteeCache.Keys())), "Incorrect key size")
+	assert.Equal(t, maxCommitteesCacheSize, len(cache.CommitteeCache.Keys()), "Incorrect key size")
 }
--- a/beacon-chain/cache/committee_test.go
+++ b/beacon-chain/cache/committee_test.go
@@ -102,7 +102,7 @@ func TestCommitteeCache_CanRotate(t *testing.T) {
 	}

 	k := cache.CommitteeCache.Keys()
-	assert.Equal(t, maxCommitteesCacheSize, uint64(len(k)))
+	assert.Equal(t, maxCommitteesCacheSize, len(k))

 	sort.Slice(k, func(i, j int) bool {
 		return k[i].(string) < k[j].(string)
--- a/beacon-chain/cache/depositcache/BUILD.bazel
+++ b/beacon-chain/cache/depositcache/BUILD.bazel
@@ -8,8 +8,12 @@ go_library(
        "pending_deposits.go",
    ],
    importpath = "github.com/prysmaticlabs/prysm/beacon-chain/cache/depositcache",
-    visibility = ["//beacon-chain:__subpackages__"],
+    visibility = [
+        "//beacon-chain:__subpackages__",
+        "//testing/spectest:__subpackages__",
+    ],
    deps = [
+        "//config/fieldparams:go_default_library",
        "//config/params:go_default_library",
        "//container/trie:go_default_library",
        "//crypto/hash:go_default_library",
--- a/beacon-chain/cache/depositcache/deposits_cache.go
+++ b/beacon-chain/cache/depositcache/deposits_cache.go
@@ -5,7 +5,6 @@
 package depositcache

 import (
-	"bytes"
 	"context"
 	"encoding/hex"
 	"math/big"
@@ -15,10 +14,10 @@ import (
 	"github.com/pkg/errors"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
+	fieldparams "github.com/prysmaticlabs/prysm/config/fieldparams"
 	"github.com/prysmaticlabs/prysm/config/params"
 	"github.com/prysmaticlabs/prysm/container/trie"
 	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
-	dbpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
 	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
 	"github.com/sirupsen/logrus"
 	"go.opencensus.io/trace"
@@ -51,9 +50,10 @@ type FinalizedDeposits struct {
 // stores all the deposit related data that is required by the beacon-node.
 type DepositCache struct {
 	// Beacon chain deposits in memory.
-	pendingDeposits   []*dbpb.DepositContainer
-	deposits          []*dbpb.DepositContainer
+	pendingDeposits   []*ethpb.DepositContainer
+	deposits          []*ethpb.DepositContainer
 	finalizedDeposits *FinalizedDeposits
+	depositsByKey     map[[fieldparams.BLSPubkeyLength]byte][]*ethpb.DepositContainer
 	depositsLock      sync.RWMutex
 }

@@ -67,8 +67,9 @@ func New() (*DepositCache, error) {
 	// finalizedDeposits.MerkleTrieIndex is initialized to -1 because it represents the index of the last trie item.
 	// Inserting the first item into the trie will set the value of the index to 0.
 	return &DepositCache{
-		pendingDeposits:   []*dbpb.DepositContainer{},
-		deposits:          []*dbpb.DepositContainer{},
+		pendingDeposits:   []*ethpb.DepositContainer{},
+		deposits:          []*ethpb.DepositContainer{},
+		depositsByKey:     map[[fieldparams.BLSPubkeyLength]byte][]*ethpb.DepositContainer{},
 		finalizedDeposits: &FinalizedDeposits{Deposits: finalizedDepositsTrie, MerkleTrieIndex: -1},
 	}, nil
 }
@@ -76,7 +77,7 @@ func New() (*DepositCache, error) {
 // InsertDeposit into the database. If deposit or block number are nil
 // then this method does nothing.
 func (dc *DepositCache) InsertDeposit(ctx context.Context, d *ethpb.Deposit, blockNum uint64, index int64, depositRoot [32]byte) error {
-	ctx, span := trace.StartSpan(ctx, "DepositsCache.InsertDeposit")
+	_, span := trace.StartSpan(ctx, "DepositsCache.InsertDeposit")
 	defer span.End()
 	if d == nil {
 		log.WithFields(logrus.Fields{
@@ -95,29 +96,41 @@ func (dc *DepositCache) InsertDeposit(ctx context.Context, d *ethpb.Deposit, blo
 	}
 	// Keep the slice sorted on insertion in order to avoid costly sorting on retrieval.
 	heightIdx := sort.Search(len(dc.deposits), func(i int) bool { return dc.deposits[i].Index >= index })
+	depCtr := &ethpb.DepositContainer{Deposit: d, Eth1BlockHeight: blockNum, DepositRoot: depositRoot[:], Index: index}
 	newDeposits := append(
-		[]*dbpb.DepositContainer{{Deposit: d, Eth1BlockHeight: blockNum, DepositRoot: depositRoot[:], Index: index}},
+		[]*ethpb.DepositContainer{depCtr},
 		dc.deposits[heightIdx:]...)
 	dc.deposits = append(dc.deposits[:heightIdx], newDeposits...)
+	// Append the deposit to our map, in the event no deposits
+	// exist for the pubkey , it is simply added to the map.
+	pubkey := bytesutil.ToBytes48(d.Data.PublicKey)
+	dc.depositsByKey[pubkey] = append(dc.depositsByKey[pubkey], depCtr)
 	historicalDepositsCount.Inc()
 	return nil
 }

 // InsertDepositContainers inserts a set of deposit containers into our deposit cache.
-func (dc *DepositCache) InsertDepositContainers(ctx context.Context, ctrs []*dbpb.DepositContainer) {
-	ctx, span := trace.StartSpan(ctx, "DepositsCache.InsertDepositContainers")
+func (dc *DepositCache) InsertDepositContainers(ctx context.Context, ctrs []*ethpb.DepositContainer) {
+	_, span := trace.StartSpan(ctx, "DepositsCache.InsertDepositContainers")
 	defer span.End()
 	dc.depositsLock.Lock()
 	defer dc.depositsLock.Unlock()

 	sort.SliceStable(ctrs, func(i int, j int) bool { return ctrs[i].Index < ctrs[j].Index })
 	dc.deposits = ctrs
+	for _, c := range ctrs {
+		// Use a new value, as the reference
+		// of c changes in the next iteration.
+		newPtr := c
+		pKey := bytesutil.ToBytes48(newPtr.Deposit.Data.PublicKey)
+		dc.depositsByKey[pKey] = append(dc.depositsByKey[pKey], newPtr)
+	}
 	historicalDepositsCount.Add(float64(len(ctrs)))
 }

 // InsertFinalizedDeposits inserts deposits up to eth1DepositIndex (inclusive) into the finalized deposits cache.
 func (dc *DepositCache) InsertFinalizedDeposits(ctx context.Context, eth1DepositIndex int64) {
-	ctx, span := trace.StartSpan(ctx, "DepositsCache.InsertFinalizedDeposits")
+	_, span := trace.StartSpan(ctx, "DepositsCache.InsertFinalizedDeposits")
 	defer span.End()
 	dc.depositsLock.Lock()
 	defer dc.depositsLock.Unlock()
@@ -136,7 +149,10 @@ func (dc *DepositCache) InsertFinalizedDeposits(ctx context.Context, eth1Deposit
 			log.WithError(err).Error("Could not hash deposit data. Finalized deposit cache not updated.")
 			return
 		}
-		depositTrie.Insert(depHash[:], insertIndex)
+		if err = depositTrie.Insert(depHash[:], insertIndex); err != nil {
+			log.WithError(err).Error("Could not insert deposit hash")
+			return
+		}
 		insertIndex++
 	}

@@ -147,8 +163,8 @@ func (dc *DepositCache) InsertFinalizedDeposits(ctx context.Context, eth1Deposit
 }

 // AllDepositContainers returns all historical deposit containers.
-func (dc *DepositCache) AllDepositContainers(ctx context.Context) []*dbpb.DepositContainer {
-	ctx, span := trace.StartSpan(ctx, "DepositsCache.AllDepositContainers")
+func (dc *DepositCache) AllDepositContainers(ctx context.Context) []*ethpb.DepositContainer {
+	_, span := trace.StartSpan(ctx, "DepositsCache.AllDepositContainers")
 	defer span.End()
 	dc.depositsLock.RLock()
 	defer dc.depositsLock.RUnlock()
@@ -159,11 +175,15 @@ func (dc *DepositCache) AllDepositContainers(ctx context.Context) []*dbpb.Deposi
 // AllDeposits returns a list of historical deposits until the given block number
 // (inclusive). If no block is specified then this method returns all historical deposits.
 func (dc *DepositCache) AllDeposits(ctx context.Context, untilBlk *big.Int) []*ethpb.Deposit {
-	ctx, span := trace.StartSpan(ctx, "DepositsCache.AllDeposits")
+	_, span := trace.StartSpan(ctx, "DepositsCache.AllDeposits")
 	defer span.End()
 	dc.depositsLock.RLock()
 	defer dc.depositsLock.RUnlock()

+	return dc.allDeposits(untilBlk)
+}
+
+func (dc *DepositCache) allDeposits(untilBlk *big.Int) []*ethpb.Deposit {
 	var deposits []*ethpb.Deposit
 	for _, ctnr := range dc.deposits {
 		if untilBlk == nil || untilBlk.Uint64() >= ctnr.Eth1BlockHeight {
@@ -176,7 +196,7 @@ func (dc *DepositCache) AllDeposits(ctx context.Context, untilBlk *big.Int) []*e
 // DepositsNumberAndRootAtHeight returns number of deposits made up to blockheight and the
 // root that corresponds to the latest deposit at that blockheight.
 func (dc *DepositCache) DepositsNumberAndRootAtHeight(ctx context.Context, blockHeight *big.Int) (uint64, [32]byte) {
-	ctx, span := trace.StartSpan(ctx, "DepositsCache.DepositsNumberAndRootAtHeight")
+	_, span := trace.StartSpan(ctx, "DepositsCache.DepositsNumberAndRootAtHeight")
 	defer span.End()
 	dc.depositsLock.RLock()
 	defer dc.depositsLock.RUnlock()
@@ -192,26 +212,28 @@ func (dc *DepositCache) DepositsNumberAndRootAtHeight(ctx context.Context, block
 // DepositByPubkey looks through historical deposits and finds one which contains
 // a certain public key within its deposit data.
 func (dc *DepositCache) DepositByPubkey(ctx context.Context, pubKey []byte) (*ethpb.Deposit, *big.Int) {
-	ctx, span := trace.StartSpan(ctx, "DepositsCache.DepositByPubkey")
+	_, span := trace.StartSpan(ctx, "DepositsCache.DepositByPubkey")
 	defer span.End()
 	dc.depositsLock.RLock()
 	defer dc.depositsLock.RUnlock()

 	var deposit *ethpb.Deposit
 	var blockNum *big.Int
-	for _, ctnr := range dc.deposits {
-		if bytes.Equal(ctnr.Deposit.Data.PublicKey, pubKey) {
-			deposit = ctnr.Deposit
-			blockNum = big.NewInt(int64(ctnr.Eth1BlockHeight))
-			break
-		}
+	deps, ok := dc.depositsByKey[bytesutil.ToBytes48(pubKey)]
+	if !ok || len(deps) == 0 {
+		return deposit, blockNum
 	}
+	// We always return the first deposit if a particular
+	// validator key has multiple deposits assigned to
+	// it.
+	deposit = deps[0].Deposit
+	blockNum = big.NewInt(int64(deps[0].Eth1BlockHeight))
 	return deposit, blockNum
 }

 // FinalizedDeposits returns the finalized deposits trie.
 func (dc *DepositCache) FinalizedDeposits(ctx context.Context) *FinalizedDeposits {
-	ctx, span := trace.StartSpan(ctx, "DepositsCache.FinalizedDeposits")
+	_, span := trace.StartSpan(ctx, "DepositsCache.FinalizedDeposits")
 	defer span.End()
 	dc.depositsLock.RLock()
 	defer dc.depositsLock.RUnlock()
@@ -231,7 +253,7 @@ func (dc *DepositCache) NonFinalizedDeposits(ctx context.Context, untilBlk *big.
 	defer dc.depositsLock.RUnlock()

 	if dc.finalizedDeposits == nil {
-		return dc.AllDeposits(ctx, untilBlk)
+		return dc.allDeposits(untilBlk)
 	}

 	lastFinalizedDepositIndex := dc.finalizedDeposits.MerkleTrieIndex
--- a/beacon-chain/cache/depositcache/deposits_cache_test.go
+++ b/beacon-chain/cache/depositcache/deposits_cache_test.go
@@ -10,7 +10,6 @@ import (
 	"github.com/prysmaticlabs/prysm/config/params"
 	"github.com/prysmaticlabs/prysm/container/trie"
 	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
-	dbpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
 	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
 	"github.com/prysmaticlabs/prysm/testing/assert"
 	"github.com/prysmaticlabs/prysm/testing/require"
@@ -44,31 +43,31 @@ func TestInsertDeposit_MaintainsSortedOrderByIndex(t *testing.T) {
 	}{
 		{
 			blkNum:      0,
-			deposit:     &ethpb.Deposit{},
+			deposit:     &ethpb.Deposit{Data: &ethpb.Deposit_Data{PublicKey: []byte{'A'}}},
 			index:       0,
 			expectedErr: "",
 		},
 		{
 			blkNum:      0,
-			deposit:     &ethpb.Deposit{},
+			deposit:     &ethpb.Deposit{Data: &ethpb.Deposit_Data{PublicKey: []byte{'B'}}},
 			index:       3,
 			expectedErr: "wanted deposit with index 1 to be inserted but received 3",
 		},
 		{
 			blkNum:      0,
-			deposit:     &ethpb.Deposit{},
+			deposit:     &ethpb.Deposit{Data: &ethpb.Deposit_Data{PublicKey: []byte{'C'}}},
 			index:       1,
 			expectedErr: "",
 		},
 		{
 			blkNum:      0,
-			deposit:     &ethpb.Deposit{},
+			deposit:     &ethpb.Deposit{Data: &ethpb.Deposit_Data{PublicKey: []byte{'D'}}},
 			index:       4,
 			expectedErr: "wanted deposit with index 2 to be inserted but received 4",
 		},
 		{
 			blkNum:      0,
-			deposit:     &ethpb.Deposit{},
+			deposit:     &ethpb.Deposit{Data: &ethpb.Deposit_Data{PublicKey: []byte{'E'}}},
 			index:       2,
 			expectedErr: "",
 		},
@@ -93,7 +92,7 @@ func TestAllDeposits_ReturnsAllDeposits(t *testing.T) {
 	dc, err := New()
 	require.NoError(t, err)

-	deposits := []*dbpb.DepositContainer{
+	deposits := []*ethpb.DepositContainer{
 		{
 			Eth1BlockHeight: 10,
 			Deposit:         &ethpb.Deposit{},
@@ -133,7 +132,7 @@ func TestAllDeposits_FiltersDepositUpToAndIncludingBlockNumber(t *testing.T) {
 	dc, err := New()
 	require.NoError(t, err)

-	deposits := []*dbpb.DepositContainer{
+	deposits := []*ethpb.DepositContainer{
 		{
 			Eth1BlockHeight: 10,
 			Deposit:         &ethpb.Deposit{},
@@ -174,7 +173,7 @@ func TestDepositsNumberAndRootAtHeight(t *testing.T) {
 	t.Run("requesting_last_item_works", func(t *testing.T) {
 		dc, err := New()
 		require.NoError(t, err)
-		dc.deposits = []*dbpb.DepositContainer{
+		dc.deposits = []*ethpb.DepositContainer{
 			{
 				Eth1BlockHeight: 10,
 				Index:           0,
@@ -205,7 +204,7 @@ func TestDepositsNumberAndRootAtHeight(t *testing.T) {
 		dc, err := New()
 		require.NoError(t, err)

-		dc.deposits = []*dbpb.DepositContainer{
+		dc.deposits = []*ethpb.DepositContainer{
 			{
 				Eth1BlockHeight: 10,
 				Index:           0,
@@ -221,7 +220,7 @@ func TestDepositsNumberAndRootAtHeight(t *testing.T) {
 		dc, err := New()
 		require.NoError(t, err)

-		dc.deposits = []*dbpb.DepositContainer{
+		dc.deposits = []*ethpb.DepositContainer{
 			{
 				Eth1BlockHeight: 8,
 				Index:           0,
@@ -247,7 +246,7 @@ func TestDepositsNumberAndRootAtHeight(t *testing.T) {
 		dc, err := New()
 		require.NoError(t, err)

-		dc.deposits = []*dbpb.DepositContainer{
+		dc.deposits = []*ethpb.DepositContainer{
 			{
 				Eth1BlockHeight: 8,
 				Index:           0,
@@ -263,7 +262,7 @@ func TestDepositsNumberAndRootAtHeight(t *testing.T) {
 		dc, err := New()
 		require.NoError(t, err)

-		dc.deposits = []*dbpb.DepositContainer{
+		dc.deposits = []*ethpb.DepositContainer{
 			{
 				Eth1BlockHeight: 8,
 				Index:           0,
@@ -279,7 +278,7 @@ func TestDepositsNumberAndRootAtHeight(t *testing.T) {
 		dc, err := New()
 		require.NoError(t, err)

-		dc.deposits = []*dbpb.DepositContainer{
+		dc.deposits = []*ethpb.DepositContainer{
 			{
 				Eth1BlockHeight: 8,
 				Index:           0,
@@ -316,8 +315,7 @@ func TestDepositsNumberAndRootAtHeight(t *testing.T) {
 func TestDepositByPubkey_ReturnsFirstMatchingDeposit(t *testing.T) {
 	dc, err := New()
 	require.NoError(t, err)
-
-	dc.deposits = []*dbpb.DepositContainer{
+	ctrs := []*ethpb.DepositContainer{
 		{
 			Eth1BlockHeight: 9,
 			Deposit: &ethpb.Deposit{
@@ -359,6 +357,7 @@ func TestDepositByPubkey_ReturnsFirstMatchingDeposit(t *testing.T) {
 			},
 		},
 	}
+	dc.InsertDepositContainers(context.Background(), ctrs)

 	pk1 := bytesutil.PadTo([]byte("pk1"), 48)
 	dep, blkNum := dc.DepositByPubkey(context.Background(), pk1)
@@ -374,7 +373,7 @@ func TestFinalizedDeposits_DepositsCachedCorrectly(t *testing.T) {
 	dc, err := New()
 	require.NoError(t, err)

-	finalizedDeposits := []*dbpb.DepositContainer{
+	finalizedDeposits := []*ethpb.DepositContainer{
 		{
 			Deposit: &ethpb.Deposit{
 				Data: &ethpb.Deposit_Data{
@@ -406,7 +405,7 @@ func TestFinalizedDeposits_DepositsCachedCorrectly(t *testing.T) {
 			Index: 2,
 		},
 	}
-	dc.deposits = append(finalizedDeposits, &dbpb.DepositContainer{
+	dc.deposits = append(finalizedDeposits, &ethpb.DepositContainer{
 		Deposit: &ethpb.Deposit{
 			Data: &ethpb.Deposit_Data{
 				PublicKey:             bytesutil.PadTo([]byte{3}, 48),
@@ -438,7 +437,7 @@ func TestFinalizedDeposits_UtilizesPreviouslyCachedDeposits(t *testing.T) {
 	dc, err := New()
 	require.NoError(t, err)

-	oldFinalizedDeposits := []*dbpb.DepositContainer{
+	oldFinalizedDeposits := []*ethpb.DepositContainer{
 		{
 			Deposit: &ethpb.Deposit{
 				Data: &ethpb.Deposit_Data{
@@ -460,7 +459,7 @@ func TestFinalizedDeposits_UtilizesPreviouslyCachedDeposits(t *testing.T) {
 			Index: 1,
 		},
 	}
-	newFinalizedDeposit := dbpb.DepositContainer{
+	newFinalizedDeposit := ethpb.DepositContainer{
 		Deposit: &ethpb.Deposit{
 			Data: &ethpb.Deposit_Data{
 				PublicKey:             bytesutil.PadTo([]byte{2}, 48),
@@ -473,7 +472,7 @@ func TestFinalizedDeposits_UtilizesPreviouslyCachedDeposits(t *testing.T) {
 	dc.deposits = oldFinalizedDeposits
 	dc.InsertFinalizedDeposits(context.Background(), 1)
 	// Artificially exclude old deposits so that they can only be retrieved from previously finalized deposits.
-	dc.deposits = []*dbpb.DepositContainer{&newFinalizedDeposit}
+	dc.deposits = []*ethpb.DepositContainer{&newFinalizedDeposit}

 	dc.InsertFinalizedDeposits(context.Background(), 2)

@@ -506,7 +505,7 @@ func TestNonFinalizedDeposits_ReturnsAllNonFinalizedDeposits(t *testing.T) {
 	dc, err := New()
 	require.NoError(t, err)

-	finalizedDeposits := []*dbpb.DepositContainer{
+	finalizedDeposits := []*ethpb.DepositContainer{
 		{
 			Eth1BlockHeight: 10,
 			Deposit: &ethpb.Deposit{
@@ -531,7 +530,7 @@ func TestNonFinalizedDeposits_ReturnsAllNonFinalizedDeposits(t *testing.T) {
 		},
 	}
 	dc.deposits = append(finalizedDeposits,
-		&dbpb.DepositContainer{
+		&ethpb.DepositContainer{
 			Eth1BlockHeight: 10,
 			Deposit: &ethpb.Deposit{
 				Data: &ethpb.Deposit_Data{
@@ -542,7 +541,7 @@ func TestNonFinalizedDeposits_ReturnsAllNonFinalizedDeposits(t *testing.T) {
 			},
 			Index: 2,
 		},
-		&dbpb.DepositContainer{
+		&ethpb.DepositContainer{
 			Eth1BlockHeight: 11,
 			Deposit: &ethpb.Deposit{
 				Data: &ethpb.Deposit_Data{
@@ -563,7 +562,7 @@ func TestNonFinalizedDeposits_ReturnsNonFinalizedDepositsUpToBlockNumber(t *test
 	dc, err := New()
 	require.NoError(t, err)

-	finalizedDeposits := []*dbpb.DepositContainer{
+	finalizedDeposits := []*ethpb.DepositContainer{
 		{
 			Eth1BlockHeight: 10,
 			Deposit: &ethpb.Deposit{
@@ -588,7 +587,7 @@ func TestNonFinalizedDeposits_ReturnsNonFinalizedDepositsUpToBlockNumber(t *test
 		},
 	}
 	dc.deposits = append(finalizedDeposits,
-		&dbpb.DepositContainer{
+		&ethpb.DepositContainer{
 			Eth1BlockHeight: 10,
 			Deposit: &ethpb.Deposit{
 				Data: &ethpb.Deposit_Data{
@@ -599,7 +598,7 @@ func TestNonFinalizedDeposits_ReturnsNonFinalizedDepositsUpToBlockNumber(t *test
 			},
 			Index: 2,
 		},
-		&dbpb.DepositContainer{
+		&ethpb.DepositContainer{
 			Eth1BlockHeight: 11,
 			Deposit: &ethpb.Deposit{
 				Data: &ethpb.Deposit_Data{
@@ -626,24 +625,28 @@ func TestPruneProofs_Ok(t *testing.T) {
 		index   int64
 	}{
 		{
-			blkNum:  0,
-			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
-			index:   0,
+			blkNum: 0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof(),
+				Data: &ethpb.Deposit_Data{PublicKey: bytesutil.PadTo([]byte("pk0"), 48)}},
+			index: 0,
 		},
 		{
-			blkNum:  0,
-			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
-			index:   1,
+			blkNum: 0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof(),
+				Data: &ethpb.Deposit_Data{PublicKey: bytesutil.PadTo([]byte("pk1"), 48)}},
+			index: 1,
 		},
 		{
-			blkNum:  0,
-			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
-			index:   2,
+			blkNum: 0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof(),
+				Data: &ethpb.Deposit_Data{PublicKey: bytesutil.PadTo([]byte("pk2"), 48)}},
+			index: 2,
 		},
 		{
-			blkNum:  0,
-			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
-			index:   3,
+			blkNum: 0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof(),
+				Data: &ethpb.Deposit_Data{PublicKey: bytesutil.PadTo([]byte("pk3"), 48)}},
+			index: 3,
 		},
 	}

@@ -669,24 +672,26 @@ func TestPruneProofs_SomeAlreadyPruned(t *testing.T) {
 		index   int64
 	}{
 		{
-			blkNum:  0,
-			deposit: &ethpb.Deposit{Proof: nil},
-			index:   0,
+			blkNum: 0,
+			deposit: &ethpb.Deposit{Proof: nil, Data: &ethpb.Deposit_Data{
+				PublicKey: bytesutil.PadTo([]byte("pk0"), 48)}},
+			index: 0,
+		},
+		{
+			blkNum: 0,
+			deposit: &ethpb.Deposit{Proof: nil, Data: &ethpb.Deposit_Data{
+				PublicKey: bytesutil.PadTo([]byte("pk1"), 48)}}, index: 1,
 		},
 		{
 			blkNum:  0,
-			deposit: &ethpb.Deposit{Proof: nil},
-			index:   1,
-		},
-		{
-			blkNum:  0,
-			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
+			deposit: &ethpb.Deposit{Proof: makeDepositProof(), Data: &ethpb.Deposit_Data{PublicKey: bytesutil.PadTo([]byte("pk2"), 48)}},
 			index:   2,
 		},
 		{
-			blkNum:  0,
-			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
-			index:   3,
+			blkNum: 0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof(),
+				Data: &ethpb.Deposit_Data{PublicKey: bytesutil.PadTo([]byte("pk3"), 48)}},
+			index: 3,
 		},
 	}

@@ -709,24 +714,28 @@ func TestPruneProofs_PruneAllWhenDepositIndexTooBig(t *testing.T) {
 		index   int64
 	}{
 		{
-			blkNum:  0,
-			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
-			index:   0,
+			blkNum: 0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof(),
+				Data: &ethpb.Deposit_Data{PublicKey: bytesutil.PadTo([]byte("pk0"), 48)}},
+			index: 0,
 		},
 		{
-			blkNum:  0,
-			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
-			index:   1,
+			blkNum: 0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof(),
+				Data: &ethpb.Deposit_Data{PublicKey: bytesutil.PadTo([]byte("pk1"), 48)}},
+			index: 1,
 		},
 		{
-			blkNum:  0,
-			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
-			index:   2,
+			blkNum: 0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof(),
+				Data: &ethpb.Deposit_Data{PublicKey: bytesutil.PadTo([]byte("pk2"), 48)}},
+			index: 2,
 		},
 		{
-			blkNum:  0,
-			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
-			index:   3,
+			blkNum: 0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof(),
+				Data: &ethpb.Deposit_Data{PublicKey: bytesutil.PadTo([]byte("pk3"), 48)}},
+			index: 3,
 		},
 	}

@@ -752,24 +761,28 @@ func TestPruneProofs_CorrectlyHandleLastIndex(t *testing.T) {
 		index   int64
 	}{
 		{
-			blkNum:  0,
-			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
-			index:   0,
+			blkNum: 0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof(),
+				Data: &ethpb.Deposit_Data{PublicKey: bytesutil.PadTo([]byte("pk0"), 48)}},
+			index: 0,
 		},
 		{
-			blkNum:  0,
-			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
-			index:   1,
+			blkNum: 0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof(),
+				Data: &ethpb.Deposit_Data{PublicKey: bytesutil.PadTo([]byte("pk1"), 48)}},
+			index: 1,
 		},
 		{
-			blkNum:  0,
-			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
-			index:   2,
+			blkNum: 0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof(),
+				Data: &ethpb.Deposit_Data{PublicKey: bytesutil.PadTo([]byte("pk2"), 48)}},
+			index: 2,
 		},
 		{
-			blkNum:  0,
-			deposit: &ethpb.Deposit{Proof: makeDepositProof()},
-			index:   3,
+			blkNum: 0,
+			deposit: &ethpb.Deposit{Proof: makeDepositProof(),
+				Data: &ethpb.Deposit_Data{PublicKey: bytesutil.PadTo([]byte("pk3"), 48)}},
+			index: 3,
 		},
 	}

@@ -785,6 +798,36 @@ func TestPruneProofs_CorrectlyHandleLastIndex(t *testing.T) {
 	assert.DeepEqual(t, [][]byte(nil), dc.deposits[3].Deposit.Proof)
 }

+func TestDepositMap_WorksCorrectly(t *testing.T) {
+	dc, err := New()
+	require.NoError(t, err)
+
+	pk0 := bytesutil.PadTo([]byte("pk0"), 48)
+	dep, _ := dc.DepositByPubkey(context.Background(), pk0)
+	var nilDep *ethpb.Deposit
+	assert.DeepEqual(t, nilDep, dep)
+
+	dep = &ethpb.Deposit{Proof: makeDepositProof(), Data: &ethpb.Deposit_Data{PublicKey: pk0, Amount: 1000}}
+	assert.NoError(t, dc.InsertDeposit(context.Background(), dep, 1000, 0, [32]byte{}))
+
+	dep, _ = dc.DepositByPubkey(context.Background(), pk0)
+	assert.NotEqual(t, nilDep, dep)
+	assert.Equal(t, uint64(1000), dep.Data.Amount)
+
+	dep = &ethpb.Deposit{Proof: makeDepositProof(), Data: &ethpb.Deposit_Data{PublicKey: pk0, Amount: 10000}}
+	assert.NoError(t, dc.InsertDeposit(context.Background(), dep, 1000, 1, [32]byte{}))
+
+	// Make sure we have the same deposit returned over here.
+	dep, _ = dc.DepositByPubkey(context.Background(), pk0)
+	assert.NotEqual(t, nilDep, dep)
+	assert.Equal(t, uint64(1000), dep.Data.Amount)
+
+	// Make sure another key doesn't work.
+	pk1 := bytesutil.PadTo([]byte("pk1"), 48)
+	dep, _ = dc.DepositByPubkey(context.Background(), pk1)
+	assert.DeepEqual(t, nilDep, dep)
+}
+
 func makeDepositProof() [][]byte {
 	proof := make([][]byte, int(params.BeaconConfig().DepositContractTreeDepth)+1)
 	for i := range proof {
--- a/beacon-chain/cache/depositcache/pending_deposits.go
+++ b/beacon-chain/cache/depositcache/pending_deposits.go
@@ -8,7 +8,6 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
 	"github.com/prysmaticlabs/prysm/crypto/hash"
-	dbpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
 	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
 	"github.com/sirupsen/logrus"
 	"go.opencensus.io/trace"
@@ -24,13 +23,13 @@ var (
 // PendingDepositsFetcher specifically outlines a struct that can retrieve deposits
 // which have not yet been included in the chain.
 type PendingDepositsFetcher interface {
-	PendingContainers(ctx context.Context, untilBlk *big.Int) []*dbpb.DepositContainer
+	PendingContainers(ctx context.Context, untilBlk *big.Int) []*ethpb.DepositContainer
 }

 // InsertPendingDeposit into the database. If deposit or block number are nil
 // then this method does nothing.
 func (dc *DepositCache) InsertPendingDeposit(ctx context.Context, d *ethpb.Deposit, blockNum uint64, index int64, depositRoot [32]byte) {
-	ctx, span := trace.StartSpan(ctx, "DepositsCache.InsertPendingDeposit")
+	_, span := trace.StartSpan(ctx, "DepositsCache.InsertPendingDeposit")
 	defer span.End()
 	if d == nil {
 		log.WithFields(logrus.Fields{
@@ -42,7 +41,7 @@ func (dc *DepositCache) InsertPendingDeposit(ctx context.Context, d *ethpb.Depos
 	dc.depositsLock.Lock()
 	defer dc.depositsLock.Unlock()
 	dc.pendingDeposits = append(dc.pendingDeposits,
-		&dbpb.DepositContainer{Deposit: d, Eth1BlockHeight: blockNum, Index: index, DepositRoot: depositRoot[:]})
+		&ethpb.DepositContainer{Deposit: d, Eth1BlockHeight: blockNum, Index: index, DepositRoot: depositRoot[:]})
 	pendingDepositsCount.Inc()
 	span.AddAttributes(trace.Int64Attribute("count", int64(len(dc.pendingDeposits))))
 }
@@ -66,13 +65,13 @@ func (dc *DepositCache) PendingDeposits(ctx context.Context, untilBlk *big.Int)

 // PendingContainers returns a list of deposit containers until the given block number
 // (inclusive).
-func (dc *DepositCache) PendingContainers(ctx context.Context, untilBlk *big.Int) []*dbpb.DepositContainer {
-	ctx, span := trace.StartSpan(ctx, "DepositsCache.PendingDeposits")
+func (dc *DepositCache) PendingContainers(ctx context.Context, untilBlk *big.Int) []*ethpb.DepositContainer {
+	_, span := trace.StartSpan(ctx, "DepositsCache.PendingDeposits")
 	defer span.End()
 	dc.depositsLock.RLock()
 	defer dc.depositsLock.RUnlock()

-	var depositCntrs []*dbpb.DepositContainer
+	var depositCntrs []*ethpb.DepositContainer
 	for _, ctnr := range dc.pendingDeposits {
 		if untilBlk == nil || untilBlk.Uint64() >= ctnr.Eth1BlockHeight {
 			depositCntrs = append(depositCntrs, ctnr)
@@ -91,7 +90,7 @@ func (dc *DepositCache) PendingContainers(ctx context.Context, untilBlk *big.Int
 // RemovePendingDeposit from the database. The deposit is indexed by the
 // Index. This method does nothing if deposit ptr is nil.
 func (dc *DepositCache) RemovePendingDeposit(ctx context.Context, d *ethpb.Deposit) {
-	ctx, span := trace.StartSpan(ctx, "DepositsCache.RemovePendingDeposit")
+	_, span := trace.StartSpan(ctx, "DepositsCache.RemovePendingDeposit")
 	defer span.End()

 	if d == nil {
@@ -129,7 +128,7 @@ func (dc *DepositCache) RemovePendingDeposit(ctx context.Context, d *ethpb.Depos

 // PrunePendingDeposits removes any deposit which is older than the given deposit merkle tree index.
 func (dc *DepositCache) PrunePendingDeposits(ctx context.Context, merkleTreeIndex int64) {
-	ctx, span := trace.StartSpan(ctx, "DepositsCache.PrunePendingDeposits")
+	_, span := trace.StartSpan(ctx, "DepositsCache.PrunePendingDeposits")
 	defer span.End()

 	if merkleTreeIndex == 0 {
@@ -140,7 +139,7 @@ func (dc *DepositCache) PrunePendingDeposits(ctx context.Context, merkleTreeInde
 	dc.depositsLock.Lock()
 	defer dc.depositsLock.Unlock()

-	var cleanDeposits []*dbpb.DepositContainer
+	var cleanDeposits []*ethpb.DepositContainer
 	for _, dp := range dc.pendingDeposits {
 		if dp.Index >= merkleTreeIndex {
 			cleanDeposits = append(cleanDeposits, dp)
--- a/beacon-chain/cache/depositcache/pending_deposits_test.go
+++ b/beacon-chain/cache/depositcache/pending_deposits_test.go
@@ -6,7 +6,6 @@ import (
 	"testing"

 	"github.com/prysmaticlabs/prysm/encoding/bytesutil"
-	dbpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
 	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
 	"github.com/prysmaticlabs/prysm/testing/assert"
 	"google.golang.org/protobuf/proto"
@@ -42,7 +41,7 @@ func TestRemovePendingDeposit_OK(t *testing.T) {
 	}
 	depToRemove := &ethpb.Deposit{Proof: proof1, Data: data}
 	otherDep := &ethpb.Deposit{Proof: proof2, Data: data}
-	db.pendingDeposits = []*dbpb.DepositContainer{
+	db.pendingDeposits = []*ethpb.DepositContainer{
 		{Deposit: depToRemove, Index: 1},
 		{Deposit: otherDep, Index: 5},
 	}
@@ -55,7 +54,7 @@ func TestRemovePendingDeposit_OK(t *testing.T) {

 func TestRemovePendingDeposit_IgnoresNilDeposit(t *testing.T) {
 	dc := DepositCache{}
-	dc.pendingDeposits = []*dbpb.DepositContainer{{Deposit: &ethpb.Deposit{}}}
+	dc.pendingDeposits = []*ethpb.DepositContainer{{Deposit: &ethpb.Deposit{}}}
 	dc.RemovePendingDeposit(context.Background(), nil /*deposit*/)
 	assert.Equal(t, 1, len(dc.pendingDeposits), "Deposit unexpectedly removed")
 }
@@ -79,7 +78,7 @@ func TestPendingDeposit_RoundTrip(t *testing.T) {
 func TestPendingDeposits_OK(t *testing.T) {
 	dc := DepositCache{}

-	dc.pendingDeposits = []*dbpb.DepositContainer{
+	dc.pendingDeposits = []*ethpb.DepositContainer{
 		{Eth1BlockHeight: 2, Deposit: &ethpb.Deposit{Proof: [][]byte{[]byte("A")}}},
 		{Eth1BlockHeight: 4, Deposit: &ethpb.Deposit{Proof: [][]byte{[]byte("B")}}},
 		{Eth1BlockHeight: 6, Deposit: &ethpb.Deposit{Proof: [][]byte{[]byte("c")}}},
@@ -99,7 +98,7 @@ func TestPendingDeposits_OK(t *testing.T) {
 func TestPrunePendingDeposits_ZeroMerkleIndex(t *testing.T) {
 	dc := DepositCache{}

-	dc.pendingDeposits = []*dbpb.DepositContainer{
+	dc.pendingDeposits = []*ethpb.DepositContainer{
 		{Eth1BlockHeight: 2, Index: 2},
 		{Eth1BlockHeight: 4, Index: 4},
 		{Eth1BlockHeight: 6, Index: 6},
@@ -109,7 +108,7 @@ func TestPrunePendingDeposits_ZeroMerkleIndex(t *testing.T) {
 	}

 	dc.PrunePendingDeposits(context.Background(), 0)
-	expected := []*dbpb.DepositContainer{
+	expected := []*ethpb.DepositContainer{
 		{Eth1BlockHeight: 2, Index: 2},
 		{Eth1BlockHeight: 4, Index: 4},
 		{Eth1BlockHeight: 6, Index: 6},
@@ -123,7 +122,7 @@ func TestPrunePendingDeposits_ZeroMerkleIndex(t *testing.T) {
 func TestPrunePendingDeposits_OK(t *testing.T) {
 	dc := DepositCache{}

-	dc.pendingDeposits = []*dbpb.DepositContainer{
+	dc.pendingDeposits = []*ethpb.DepositContainer{
 		{Eth1BlockHeight: 2, Index: 2},
 		{Eth1BlockHeight: 4, Index: 4},
 		{Eth1BlockHeight: 6, Index: 6},
@@ -133,7 +132,7 @@ func TestPrunePendingDeposits_OK(t *testing.T) {
 	}

 	dc.PrunePendingDeposits(context.Background(), 6)
-	expected := []*dbpb.DepositContainer{
+	expected := []*ethpb.DepositContainer{
 		{Eth1BlockHeight: 6, Index: 6},
 		{Eth1BlockHeight: 8, Index: 8},
 		{Eth1BlockHeight: 10, Index: 10},
@@ -142,7 +141,7 @@ func TestPrunePendingDeposits_OK(t *testing.T) {

 	assert.DeepEqual(t, expected, dc.pendingDeposits)

-	dc.pendingDeposits = []*dbpb.DepositContainer{
+	dc.pendingDeposits = []*ethpb.DepositContainer{
 		{Eth1BlockHeight: 2, Index: 2},
 		{Eth1BlockHeight: 4, Index: 4},
 		{Eth1BlockHeight: 6, Index: 6},
@@ -152,7 +151,7 @@ func TestPrunePendingDeposits_OK(t *testing.T) {
 	}

 	dc.PrunePendingDeposits(context.Background(), 10)
-	expected = []*dbpb.DepositContainer{
+	expected = []*ethpb.DepositContainer{
 		{Eth1BlockHeight: 10, Index: 10},
 		{Eth1BlockHeight: 12, Index: 12},
 	}
--- a/beacon-chain/cache/proposer_indices.go
+++ b/beacon-chain/cache/proposer_indices.go
@@ -1,4 +1,5 @@
-// +build !libfuzzer
+//go:build !fuzz
+// +build !fuzz

 package cache

--- a/beacon-chain/cache/proposer_indices_disabled.go
+++ b/beacon-chain/cache/proposer_indices_disabled.go
@@ -1,4 +1,5 @@
-// +build libfuzzer
+//go:build fuzz
+// +build fuzz

 // This file is used in fuzzer builds to bypass proposer indices caches.
 package cache
--- a/beacon-chain/cache/skip_slot_cache.go
+++ b/beacon-chain/cache/skip_slot_cache.go
@@ -120,26 +120,22 @@ func (c *SkipSlotCache) MarkInProgress(r [32]byte) error {

 // MarkNotInProgress will release the lock on a given request. This should be
 // called after put.
-func (c *SkipSlotCache) MarkNotInProgress(r [32]byte) error {
+func (c *SkipSlotCache) MarkNotInProgress(r [32]byte) {
 	if c.disabled {
-		return nil
+		return
 	}

 	c.lock.Lock()
 	defer c.lock.Unlock()

 	delete(c.inProgress, r)
-	return nil
 }

 // Put the response in the cache.
-func (c *SkipSlotCache) Put(_ context.Context, r [32]byte, state state.BeaconState) error {
+func (c *SkipSlotCache) Put(_ context.Context, r [32]byte, state state.BeaconState) {
 	if c.disabled {
-		return nil
+		return
 	}
-
 	// Copy state so cached value is not mutated.
 	c.cache.Add(r, state.Copy())
-
-	return nil
 }
--- a/beacon-chain/cache/skip_slot_cache_test.go
+++ b/beacon-chain/cache/skip_slot_cache_test.go
@@ -28,8 +28,8 @@ func TestSkipSlotCache_RoundTrip(t *testing.T) {
 	})
 	require.NoError(t, err)

-	require.NoError(t, c.Put(ctx, r, s))
-	require.NoError(t, c.MarkNotInProgress(r))
+	c.Put(ctx, r, s)
+	c.MarkNotInProgress(r)

 	res, err := c.Get(ctx, r)
 	require.NoError(t, err)
--- a/beacon-chain/cache/subnet_ids.go
+++ b/beacon-chain/cache/subnet_ids.go
@@ -27,7 +27,7 @@ var SubnetIDs = newSubnetIDs()
 func newSubnetIDs() *subnetIDs {
 	// Given a node can calculate committee assignments of current epoch and next epoch.
 	// Max size is set to 2 epoch length.
-	cacheSize := int(params.BeaconConfig().SlotsPerEpoch.Mul(params.BeaconConfig().MaxCommitteesPerSlot * 2))
+	cacheSize := int(params.BeaconConfig().SlotsPerEpoch.Mul(params.BeaconConfig().MaxCommitteesPerSlot * 2)) // lint:ignore uintcast -- constant values that would panic on startup if negative.
 	attesterCache := lruwrpr.New(cacheSize)
 	aggregatorCache := lruwrpr.New(cacheSize)
 	epochDuration := time.Duration(params.BeaconConfig().SlotsPerEpoch.Mul(params.BeaconConfig().SecondsPerSlot))
--- a/beacon-chain/cache/subnet_ids_test.go
+++ b/beacon-chain/cache/subnet_ids_test.go
@@ -4,6 +4,7 @@ import (
 	"testing"

 	types "github.com/prysmaticlabs/eth2-types"
+	fieldparams "github.com/prysmaticlabs/prysm/config/fieldparams"
 	"github.com/prysmaticlabs/prysm/testing/assert"
 	"github.com/prysmaticlabs/prysm/testing/require"
 )
@@ -46,12 +47,12 @@ func TestSubnetIDsCache_PersistentCommitteeRoundtrip(t *testing.T) {
 	c := newSubnetIDs()

 	for i := 0; i < 20; i++ {
-		pubkey := [48]byte{byte(i)}
+		pubkey := [fieldparams.BLSPubkeyLength]byte{byte(i)}
 		c.AddPersistentCommittee(pubkey[:], []uint64{uint64(i)}, 0)
 	}

 	for i := uint64(0); i < 20; i++ {
-		pubkey := [48]byte{byte(i)}
+		pubkey := [fieldparams.BLSPubkeyLength]byte{byte(i)}

 		idxs, ok, _ := c.GetPersistentSubnets(pubkey[:])
 		if !ok {
--- a/beacon-chain/cache/sync_committee.go
+++ b/beacon-chain/cache/sync_committee.go
@@ -1,4 +1,5 @@
-// +build !libfuzzer
+//go:build !fuzz
+// +build !fuzz

 package cache

--- a/beacon-chain/cache/sync_committee_disabled.go
+++ b/beacon-chain/cache/sync_committee_disabled.go
@@ -1,4 +1,5 @@
-// +build libfuzzer
+//go:build fuzz
+// +build fuzz

 package cache

--- a/beacon-chain/cache/sync_committee_head_state.go
+++ b/beacon-chain/cache/sync_committee_head_state.go
@@ -6,8 +6,8 @@ import (
 	lru "github.com/hashicorp/golang-lru"
 	types "github.com/prysmaticlabs/eth2-types"
 	"github.com/prysmaticlabs/prysm/beacon-chain/state"
-	stateAltair "github.com/prysmaticlabs/prysm/beacon-chain/state/v2"
 	lruwrpr "github.com/prysmaticlabs/prysm/cache/lru"
+	"github.com/prysmaticlabs/prysm/runtime/version"
 )

 // SyncCommitteeHeadStateCache for the latest head state requested by a sync committee participant.
@@ -31,10 +31,11 @@ func (c *SyncCommitteeHeadStateCache) Put(slot types.Slot, st state.BeaconState)
 	if st == nil || st.IsNil() {
 		return ErrNilValueProvided
 	}
-	_, ok := st.(*stateAltair.BeaconState)
-	if !ok {
+
+	if st.Version() == version.Phase0 {
 		return ErrIncorrectType
 	}
+
 	c.cache.Add(slot, st)
 	return nil
 }
@@ -47,9 +48,14 @@ func (c *SyncCommitteeHeadStateCache) Get(slot types.Slot) (state.BeaconState, e
 	if !exists {
 		return nil, ErrNotFound
 	}
-	st, ok := val.(*stateAltair.BeaconState)
+	st, ok := val.(state.BeaconState)
 	if !ok {
 		return nil, ErrIncorrectType
 	}
+	switch st.Version() {
+	case version.Altair, version.Bellatrix:
+	default:
+		return nil, ErrIncorrectType
+	}
 	return st, nil
 }
--- a/beacon-chain/cache/sync_committee_head_state_test.go
+++ b/beacon-chain/cache/sync_committee_head_state_test.go
@@ -7,6 +7,7 @@ import (
 	"github.com/prysmaticlabs/prysm/beacon-chain/state"
 	v1 "github.com/prysmaticlabs/prysm/beacon-chain/state/v1"
 	v2 "github.com/prysmaticlabs/prysm/beacon-chain/state/v2"
+	v3 "github.com/prysmaticlabs/prysm/beacon-chain/state/v3"
 	"github.com/prysmaticlabs/prysm/config/params"
 	ethpb "github.com/prysmaticlabs/prysm/proto/prysm/v1alpha1"
 	"github.com/prysmaticlabs/prysm/testing/require"
@@ -27,6 +28,13 @@ func TestSyncCommitteeHeadState(t *testing.T) {
 		},
 	})
 	require.NoError(t, err)
+	bellatrixState, err := v3.InitializeFromProto(&ethpb.BeaconStateBellatrix{
+		Fork: &ethpb.Fork{
+			PreviousVersion: params.BeaconConfig().GenesisForkVersion,
+			CurrentVersion:  params.BeaconConfig().GenesisForkVersion,
+		},
+	})
+	require.NoError(t, err)
 	type put struct {
 		slot  types.Slot
 		state state.BeaconState
@@ -82,6 +90,24 @@ func TestSyncCommitteeHeadState(t *testing.T) {
 			},
 			want: beaconState,
 		},
+		{
+			name: "not found when non-existent key in non-empty cache (bellatrix state)",
+			key:  types.Slot(2),
+			put: &put{
+				slot:  types.Slot(1),
+				state: bellatrixState,
+			},
+			wantErr: true,
+		},
+		{
+			name: "found with key (bellatrix state)",
+			key:  types.Slot(100),
+			put: &put{
+				slot:  types.Slot(100),
+				state: bellatrixState,
+			},
+			want: bellatrixState,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
--- a/Show More
+++ b/Show More
@@ -1 +1 @@
 .7.0
 .0.0