Single Sequencer

A single sequencer is the simplest sequencing architecture for a Rollkit-based rollup. In this model, one node (the sequencer) is responsible for ordering transactions, producing blocks, and submitting data to the data availability (DA) layer.

How the Single Sequencer Model Works

1. Transaction Submission:

   • Users submit transactions to the execution environment via RPC or other interfaces.

2. Transaction Collection and Ordering:

   • The execution environment collects incoming transactions.
   • The sequencer requests a batch of transactions from the execution environment to be included in the next block.

3. Block Production:

   • Without lazy mode: the sequencer produces new blocks at fixed intervals.
   • With lazy mode: the sequencer produces a block once either
     • enough transactions are collected
     • the lazy-mode block interval elapses More info here.
   • Each block contains a batch of ordered transactions and metadata.

4. Data Availability Posting:

   • The sequencer posts the block data to the configured DA layer (e.g., Celestia).
   • This ensures that anyone can access the data needed to reconstruct the rollup state.

5. State Update:

   • The sequencer updates the rollup state based on the new block and makes the updated state available to light clients and full nodes.

Transaction Flow Diagram

Advantages

• Simplicity: Easy to set up and operate, making it ideal for development, testing, and small-scale deployments compared to other more complex sequencers.
• Low Latency: Fast block production and transaction inclusion, since there is no consensus overhead among multiple sequencers.
• Independence from DA block time: The sequencer can produce blocks on its own schedule, without being tied to the block time of the DA layer, enabling more flexible transaction processing than DA-timed sequencers.