Flashblocks Architecture

The Flashblocks pipeline layers four new components — rollup-boost, base-builder, websocket-proxy, and base — onto Base’s existing high-availability sequencer.

Before Flashblocks

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

Component	Role
base-consensus	Consensus layer (CL) — took over from op-node after Azul.
base-reth-node	Execution layer (EL) — took over from op-geth after Azul.
op-conductor	High availability controller using Raft consensus for leader election.

One sequencer instance is the leader and produces blocks, propagating them over P2P. The other four follow and sync the chain. Leadership transfers when the current leader stops producing blocks.

With Flashblocks

Flashblocks add several new infrastructure components:

Component	Purpose	What it unlocks
rollup-boost	CL↔EL Engine API proxy.	Streams Flashblocks to the EL without modifying the CL. Provides a stable seam for future block-building changes such as multi-builder.
base-builder	Out-of-protocol builder running at 200ms cadence.	Produces sub-second Flashblocks decoupled from the EL and enables pluggable builder mechanisms.
websocket-proxy	Fan-out for the Flashblocks stream.	Lets many consumers read the stream without overwhelming the builder.
base	RPC surface that exposes preconfirmations.	Turns streamed Flashblocks into familiar RPC methods so apps and wallets can consume preconfirmed state.

Flashbots builds and maintains rollup-boost; Base maintains base-builder, the websocket-proxy, and the base component.

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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.