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Based Sequencing ​

Based sequencing is a fundamental approach to Layer 2 (L2) scaling where transaction ordering is driven by the underlying Layer 1 (L1) blockchain. This design provides key advantages over traditional L2 designs with centralized sequencers.

What is Based Sequencing? ​

A Layer 2 is considered "based" when its transaction sequencing is driven by the base Layer 1. In practice, this means:

  • Transaction ordering is determined by L1 validators
  • Anyone can permissionlessly propose the next L2 block
  • Block inclusion happens as part of normal L1 block production
  • MEV (Maximal Extractable Value) flows to L1 validators

Core Benefits ​

  1. True Decentralization

    • No single party controls transaction ordering
    • Inherits the base layer's decentralized validator set
    • Permissionless block proposal system
    • No special permissions or trusted parties needed

  2. Enhanced Security

    • Inherits 100% of L1's security guarantees
    • No escape hatches or timeout periods needed
    • Full censorship resistance from day one
    • Same liveness guarantees as L1

  3. Economic Alignment

    • MEV flows strengthen L1 security
    • No additional token needed for sequencing
    • Natural integration with L1 proposer/builder separation
    • Reduced operational complexity

How Based Sequencing Works ​

  1. Transaction Submission

    • Users submit transactions to the L2 network
    • Transactions are collected in the L2 mempool

  2. Block Production

    • L1 validators can include L2 transactions in their blocks
    • Block builders can bundle L1 and L2 transactions together
    • Anyone can propose the next L2 block

  3. Finalization

    • L2 blocks are finalized when their L1 block is finalized
    • Ordering is determined by L1 block order
    • No additional consensus mechanism needed

Challenges and Solutions ​

While based sequencing offers many benefits, it also presents some challenges:

  1. Block Time Constraints

    • L2 blocks are limited by L1 block times
    • Solved through preconfirmations for fast feedback

  2. MEV Considerations

    • Coordination between L1 and L2 MEV
    • Builders need to optimize across both layers

  3. Data Availability

    • L2 data must be published on L1
    • Can be optimized through batching and compression

These challenges are typically addressed through careful protocol design and additional mechanisms like preconfirmations.