Flashblocks Architecture

Understand the sequencer architecture and infrastructure components that power Flashblocks on Base.

Before Flashblocks

Base operates a high-availability sequencer system with five sequencer instances:

Component	Role
base-consensus	Consensus layer (CL) — replaced op-node after Azul
base-reth-node	Execution layer (EL) — replaced op-geth after Azul
op-conductor	High availability controller with Raft consensus for leader election

One sequencer instance acts as the leader, responsible for building blocks and propagating them via P2P. The remaining four act as followers that sync the chain. Leadership transfers if the current leader stops producing blocks.

With Flashblocks

Flashblocks introduce several new infrastructure components:

Component	Purpose	What It Unlocks
rollup-boost	CL↔EL Engine API proxy	Enables sharing Flashblocks with the EL without modifying the CL. Provides a stable seam for future block-building evolutions (multi-builder, etc.)
base-builder	Out-of-protocol builder at 200ms cadence	Produces the sub-second Flashblocks, decoupled from the EL. Enables pluggable builder mechanisms
websocket-proxy	Flashblocks stream fan-out	Broadcast layer so many consumers can read the stream without overwhelming the builder
base	RPC surface exposing preconfirmations	Converts streamed Flashblocks into familiar RPCs so apps and wallets can consume preconfirmation state

rollup-boost is built and maintained by Flashbots, while Base maintains base-builder, the websocket-proxy, and the base components.

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Further Reading

• Flashblocks Overview — Key concepts and transaction lifecycle
• Enable Flashblocks — Run your own Flashblocks-aware RPC node
• API Reference — RPC methods, WebSocket subscriptions, and infrastructure stream schema
• Flashblocks Deep Dive — Engineering blog post with implementation details