Astria replaces centralized sequencers, allowing many rollups to share a single decentralized network of sequencers that’s simple and permissionless to join. This shared sequencer network provides out-of-the-box censorship resistance, fast block confirmations, and atomic cross-rollup composability – all while retaining each rollup’s sovereignty.

Simultaneously, we're announcing the Astria EVM, the first rollup to be powered by the shared sequencer network. The EVM has emerged as today’s flagship VM, and there’s a clear need for it in the Celestia ecosystem which we intend to satisfy. By leveraging the shared sequencer network for fast, censorship resistant transaction ordering, and Celestia for data availability, the Astria EVM is able to overcome limitations in scalability, performance, and decentralization faced by other EVMs. Our goal is for the Astria EVM to help bootstrap Celestia’s rollup ecosystem by acting as a hub for liquidity and bridging, both in Celestia’s data availability cluster and with other ecosystems.

Centralization is antithetical to crypto. And yet, today’s rollups almost universally depend on a single sequencer. Centralized sequencers provide fast transaction confirmations and reduce costs by batching and compressing transactions. However, these benefits come at the cost of relying on a single trusted actor for liveness and censorship resistance.

Sacrificing decentralization for an improved user experience is an unacceptable Faustian bargain.

So why haven’t rollups decentralized yet? Well, it’s hard. Recruiting a diverse set of actors to participate in a network is a technical and organizational lift that takes significant time and energy. Focusing on decentralization diverts resources that would otherwise be spent improving a rollup’s core product and features. In a competitive environment, it’s not in any individual rollup’s best interest to decentralize first.

That’s why decentralization isn’t a problem that each rollup team should need to solve themselves.

**Astria tackles centralization head-on, providing rollups with a decentralized sequencer and *even better* UX. **Astria’s shared sequencer network is a middleware blockchain with its own decentralized sequencer set which accepts transactions from multiple rollups. These transactions are ordered into a single block and written to the base layer without executing them.

Rollups can retrieve blocks from Astria immediately after they’re created, without waiting for the base layer to include them. The economic weight of Astria’s decentralized sequencer set provides confidence that this transaction order is final. This “soft commitment” allows rollups to provide their end users with fast block confirmations. Alternatively, rollups can wait for blocks to be included by the base layer, giving them the strongest finality. All transactions still get this “firm commitment” at the speed of the base layer, fast pre-confirmations are just an additional feature that Astria provides to rollups if they choose to use it.

To generate a new state root, a rollup’s full nodes retrieve a block from either Astria or the base layer, check it against Astria’s fork choice rule, filter out transactions from other rollups, and apply the resultant subset of transactions to their previous state. Headers can then be generated from this state root and gossiped to light clients. Rollups of this style are termed ‘Lazy Rollups’, a nod to the Lazy Evaluation principle found in programming language theory.

Because Astria decouples ordering from execution, the network’s block producing nodes do not need to store the state of any dependent rollup, and the network is agnostic to the number of distinct rollups using it. Astria is therefore able to offer decentralization as a service to an arbitrary number of rollups. These rollups benefit from censorship resistance guarantees that can only be provided by a decentralized network, without needing to establish that network themselves. Rollups can then focus on differentiating and optimizing their state transition function, allowing them to develop unique performance characteristics to better serve a diverse range of use-cases.

Because Astria handles the transaction ordering for multiple rollups, it’s able to provide guarantees that transactions are only included as part of an atomic bundle. This allows users to specify that a transaction on Rollup A can be included in a block if and only if a different transaction on Rollup B is also included in the same block. By enabling such conditional transaction inclusion, Astria unlocks exciting possibilities such as atomic cross-rollup arbitrage.

Sovereignty is important, so rollups must be able to receive the benefits of Astria without fear of being locked in. That’s why swapping out the sequencing layer is as simple as updating a rollup node’s software to use a different fork choice rule at a chosen block height. Transaction data is stored on the base layer (eg. Celestia), and rollup full nodes hold the state and perform execution, this means there’s nothing that Astria can do to hold the rollup hostage.

Astria’s origins can be traced back to both the Cevmos project, an early attempt to build EVM-based rollups on top of Celestia, and Rollkit (f.k.a. Rollmint or Optimint), a modular development framework for Rollups. While our work on the Astria EVM has diverged from both projects, we continue to develop what we believe is the best way to deploy an EVM as a sovereign rollup on Celestia. Additionally, the Astria EVM forces us to “eat our own dogfood” by acting as a test case for how to best integrate rollups with our shared sequencer network.

Astria envisions a future where thousands of decentralized, sovereign rollups flourish, each one tailored to meet the unique requirements of different industries, applications, and use cases. To achieve this vision, we believe that deploying an economically secure, decentralized, and censorship-resistant sovereign rollup should be as easy as deploying a smart contract.

Astria's shared sequencer network plays a pivotal role in our vision by enabling rollup developers to easily integrate with a decentralized network which provides fast, censorship resistant transaction ordering, and cross-rollup composability. Streamlining the rollup development process empowers developers to create new, innovative blockchains without compromising on crypto’s core principle of decentralization.

We’re incredibly excited about this vision and are committed to working towards a future where decentralized sovereign rollups reshape the blockchain landscape, empowering users and developers alike.