One of the core promises of rollups is scalability without compromising Ethereum's neutrality and decentralisation. But many rollups today still rely on centralised sequencers—entities with privileged access to ordering transactions. While efficient, this undermines the trust-minimised ethos that makes rollups attractive in the first place.

At Spire Labs, we've been exploring a new approach to this problem with Based Rollups. As part of this journey, we're releasing our Based Stack. It's a fork of the OP Stack designed for deploying "based rollups" that inherit Ethereum's decentralisation and security guarantees without compromising on scalability or developer experience.

Two big primitive we've delivered in our based-stack is Sequencer Elections. We've tackled this by focusing on two key areas

🧾 Election Tickets

⏳ Dutch Block Auction

Together, they form a market-driven, permissionless sequencing mechanism where anyone can win the right to produce a block on the rollup and submit it to Ethereum L1.

Let's dive in!

📍 The Problem With Centralized Sequencers

Most rollups use a single operator to sequence transactions. The ones that don't usually use a permissioned set of sequencers and have some form of round-robin BFT consensus. This allows fast block times and UX improvements, but creates serious downsides:

• Censorship risk: Users are stuck if the sequencer refuses to include certain transactions.

• MEV extraction: A centralised sequencer can reorder transactions for profit.

• Trust assumptions: Users must trust an off-chain actor to behave honestly.

To fix this, we need decentralised sequencing — where many actors can compete to build and submit blocks, and no single party has control.

🧠 Enter: The Dutch Auction

The Based Stack introduces a novel mechanism to the L2 block-building process: the Dutch Auction!

This permissionless auction determines who gets the right to participate as a sequencer in future blocks.

Here's how it works:

• The auction begins at a high bid price with 32 sequencing slots for sale.

• Each block, the price decreases at configurable decay rate.

• Anyone can call the auction contract to buy up to the remaining tickets, locking in their right to build one or more future blocks at the current price they pay.

• Once purchased, that holder becomes eligible to propose a block.

• When the auction ends, soulbound NFTs are minted as election tickets to the participants who purchased tickets.

The auction decides who gets to be in sequencer pool.

🗳 Election Tickets: The Proof of Sequencer Rights

Election Tickets are tokenised rights to participate in sequencing, tightly integrated with the auction mechanism.

• The slot winners are chosen from the pool of ticket holders every epoch.

• Winning election tickets are burnt.

• The winner should submit a block for the slot they win.

• In the future, misbehaviour (like submitting an invalid block) can lead to slashing of a staked ticket.

These tickets form the backbone of trustless sequencing in the based stack. You can prove on-chain that you earned the right to submit a block. The system can enforce rules and incentives (e.g., slashing, rewards, or rebates). They unlock game-theoretic participation, as participants strategise around ticket pricing, auction timing, and MEV opportunities.

This also opens the door to further decentralisation. DAOs could subsidise ticket purchases to promote public goods infrastructure or specific applications. We belive that a liquid, permissionless market for sequencing rights will emerge on top of Ethereum. This structure enables MEV builders and relayers to engage in a secondary market with election winners.

The election process chooses when they can sequence.

🔄 How This Enables a Based Rollup

In Ethereum's L1, miners and validators compete in an open blockspace market. The Based Stack brings this ethos to L2 with election-based sequencing.

For us, the table stakes for a based rollup is one where:

• Anyone can become a sequencer through open participation.

• No entity controls ordering rights long-term.

• Consensus remains minimal, with Ethereum still securing data availability and settlement.

The Dutch auction with election ticket model is a novel mechanism for enabling this. It's simple, modular, and aligned with Ethereum's values.

🛠 Try It Out — Help Build the Future of L2 Sequencing

The initial implementation is open source and available in our github repo. If you’re launching a rollup, rethinking L2 decentralisation, or exploring new sequencing designs, we want to build with you.

Got ideas? Questions? Drop us an email or fill out this form to get building!