# The Based Path to Decentralised Sequencing *Selling Execution Tickets with a Dutch Block Auction* By [Spire Labs](https://paragraph.com/@spire) · 2025-03-26 --- 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! ![](https://storage.googleapis.com/papyrus_images/ee0cdd3c1953e04421a8fda91f74e25b.png) 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](https://github.com/spire-labs/based-stack). 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](mailto:hello@spire.dev) or fill out this [form](https://docs.google.com/forms/d/1ii4vDERJQpadOmDzCD_DpoCG9GtS8isVPUhTs17Er8k/edit) to get building! --- *Originally published on [Spire Labs](https://paragraph.com/@spire/the-based-path-to-decentralised-sequencing)*