How Far Can Decentralized Sequencers for Rollup Networks Go

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Sequencers are a core component of rollup networks, responsible for crucial operations including receiving, sorting and executing transactions, as well as submitting transaction data.

If the only sequencer in a network fails or becomes unavailable, the whole network will stop processing transactions.

However, many of the existing rollup solutions only have a single sequencer, making them far less decentralized than some centralized layer-one alternatives.

Therefore, the importance of decentralized sequencers is self-evident, and promising decentralized sequencers should effectively increase the decentralization of a network with optimized design and implementation.

Importance of sequencers

Existing rollup solutions include ZKPs (zero-knowledge proofs) based ZK-rollups and optimistic execution-based optimistic rollups.

These solutions are more scalable than monolithic layer-ones. But they still have their respective issues.

Issues with ZK-rollups

• Computational complexity – Using ZKPs to verify the correctness and legitimacy of transactions requires a significant amount of computational resources and time. This may result in transaction-processing delays and high computational costs.
• Dependency on verifiability – ZK-rollups rely on external verifiability, meaning that external supervisors are required to verify the correctness of ZK proofs. This may introduce trust issues and centralization risks.

Issues with optimistic rollups

• Reversibility – Optimistic rollups work on an ‘optimistic’ assumption that all transactions submitted are valid and conflict-free. However, if there are conflicts or invalid transactions, the entire system may have to roll back and re-execute, leading to uncertainties and processing delays.
• MEV – Optimistic rollups may face MEV (maximal extractable value) issues, such as manipulated and unfair transaction ordering.

These issues reduce the performance and security of existing rollup solutions and may impact usability and user experience.

The introduction of new designs like sequencers to improve the performance and decentralization of rollups is key to addressing these issues.

Sequencers can increase throughput and compress transaction data.

Specifically, they order transactions according to predetermined rules, which can not only enhance the efficiency and throughput of transaction processing but also reduce conflicts and competition among transactions.

Sequencers…