Shared Sequencers: An L2 Scaling Solution
Written by Jackson George
Background
Rollups–whether optimistic or zero-knowledge–were designed as solutions to alleviate scalability issues with Ethereum. As a quick reminder or for those who are not familiar, rollups settle transactions off of L1 chains while still posting a “rollup” of the transaction data on the L1, deriving security from the underlying network while reducing its transaction fees.
Within rollup architecture, sequencers perform the task of processing and ordering user transactions in blocks before they are posted to the chain; most L2s run their own proprietary sequencing solution.
The Problem
However, the fact that L2s run their own sequencers is fundamentally unscalable. If, instead, there was decentralized block production at the level of the sequencer, it could be utilized by multiple rollups as opposed to each rollup building its own sequencer network. Furthermore, from a security standpoint, single sequencers introduce single points of failure, the potential for censorship, and the potential for monopolistic pricing / price gouging.
The Solution
A decentralized sequencer network has the potential to bolster censorship resistance and enhance the resilience of sequencer operations. Establishing a shared sequencer network would foster better compatibility and interoperability between rollups and fortify resistance against MEV.
Effects on the Ecosystem
The adoption of shared sequencers can substantially improve the Web3 ecosystem. Foremost, shared sequencers foster a more cohesive ecosystem by facilitating seamless interactions and transactions between various blockchain networks and L2s, reducing fragmentation and enhancing user experiences. Additionally, the resistance to MEV manipulation, by establishing guidelines for transaction ordering within blocks, ensures a fairer and more transparent transaction processing system. The collective use of a shared set of sequencers not only reduces redundancy and wasted resources but also enhances decentralization within the space, bolstering the overall resilience and censorship resistance of the ecosystem, thus engendering greater trust among its participants. This collaborative approach further expedites scalability by alleviating the need for new chains to construct their own sequencers, thus accelerating the deployment of innovative blockchain solutions. In essence, shared sequencers represent a significant stride toward a more efficient, secure, and interconnected Web3, poised to unlock the full potential of decentralized technologies.
So…who’s building in the space?
Astria is one company building a shared sequencer network working towards the decentralization of sequencers, improved censorship resistance, fast block confirmations, and enhanced rollup composability. Astria separates the ordering and execution of transactions into different functions — the shared sequencer orders transactions for chains using it as their sequencing layer, but it does not execute or prove the transactions. Those are deferred to the chain and can be done after the fact.
Astria EVM (their own rollup) has implemented the Astria Shared Sequencer, but it doesn’t look like any other prominent rollups have adopted it yet.
Like many things in the blockchain space, the business model behind shared sequencers is still developing. Maven11, a VC who are investors in Astria, wrote a post suggesting that sequencers could collect fees based on MEV extracted, cross-chain value transferred, flat fees, and/or a percentage of cost savings vs independent networks. Low fees may be important for the growth of the rollup space: they will help attract new rollups and applications to join the network which would then create more opportunities for cross-chain MEV extraction.
Edited by Charlie Ambrose
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