Shared sequencing is an architecture in which a sequencing service or network orders transactions for more than one rollup. It changes who coordinates transaction ordering. It does not, by itself, replace each rollup’s execution, data availability, proof system, or settlement rules.
How shared sequencing works
A rollup user submits a transaction to a sequencer. With independent sequencing, each rollup has its own ordering process. In a shared design, a common service or validator network can accept transactions tagged for multiple rollups and agree on an order or slot. The rollups then obtain their own transaction data and execute it under their respective state-transition rules. Implementations differ: some separate ordering, data availability, confirmations, and execution into distinct components.
Astria’s architecture documentation, for example, describes a sequencing layer that orders rollup data, a data-availability layer, and rollup nodes that fetch and verify their data before execution. Espresso’s documentation describes sequencing and confirmations that rollups may use alongside a separate data-availability choice. These examples illustrate possible designs; their features should not be assumed to apply to every shared sequencer.
What it may enable
Coordinated ordering can make it easier to include transactions from several rollups in a related order or in a conditional bundle. That may help applications coordinate actions across rollups and can reduce dependence on one rollup operator for ordering, if the shared network itself uses a suitably decentralized consensus process. It can also create new choices about how ordering rights and any associated fees or maximal extractable value are allocated.
Ordering is not execution
Atomic inclusion means transactions are ordered or included together. It does not mean each rollup successfully executes them. A swap may revert because its price changed, its state differs from what a bundle expected, or a contract call fails. Without an additional protocol that coordinates execution and handles failures across the participating rollups, one action may succeed while another does not. Research on cross-rollup atomic transactions studies those extra coordination requirements explicitly.
Shared sequencing therefore does not automatically provide seamless cross-rollup composability, all-or-nothing settlement, censorship resistance, or fairer MEV distribution. Those outcomes depend on the sequencer’s consensus and inclusion rules, each rollup’s execution and settlement design, bridge or application support, and any forced-inclusion or escape mechanism. A shared service can also introduce common availability, governance, and economic dependencies.
How it differs from based sequencing
Based rollups use Ethereum’s block proposers or validators to sequence rollup transactions. Shared sequencing usually refers to a service or network used by multiple rollups, which may have its own consensus. Both approaches address sequencing choices, but they make different trade-offs around latency, coordination, validator incentives, and operational dependencies. Neither label alone proves that a rollup is fully decentralized.
Social Media Sentiment
A September 2024 r/ethereum discussion about shared sequencing asked whether it would resolve rollup fragmentation and raised a concern that rollup operators may not want to give up sequencing revenue. The thread is an older, small snapshot of community questions, not evidence of current consensus or project status.
Last updated: 2026-10
Related Terms
- Rollup — a scaling system that executes transactions away from Ethereum and posts data or proofs for settlement.
- Based Rollup — a rollup design that uses Ethereum block proposers for sequencing.
- MEV — value that can arise from choosing or changing transaction ordering and inclusion.
See Also
- Are Layer 2 Networks Actually Decentralized? — examines the different control points and trust assumptions in Layer 2 systems.
- Does Ethereum TPS Include Layer 2 Transactions? — explains how rollup activity relates to Ethereum’s base layer.
- What Is MEV — And Why Every Ethereum Transaction Is a Game — introduces transaction ordering incentives and their effects.
- Exchange crypto with ChangeNOW
Sources
- Ethereum.org, Optimistic Rollups — Explains rollup operators, sequencer ordering power, settlement, and forced transaction inclusion.
- Astria, Introduction and architecture — Describes one design that separates shared sequencing, data availability, rollup data retrieval, and execution.
- Espresso, Sequencing in the modular stack — Describes optional sequencing and confirmations alongside a rollup’s chosen data-availability layer.
- Kaklamanis and Zhang, “CRATE: Cross-Rollup Atomic Transaction Execution” (2025) — Studies the additional coordination needed for all-or-nothing execution across rollups.
- r/ethereum discussion, September 2024 — A small historical thread used only as an example of questions about fragmentation and operator incentives.