In April this year, Astria, a modular blockchain focused on shared sequencers, completed a $5.5 million seed round of financing led by Maven 11, with participation from 1kx, Delphi Ventures, Robot Ventures, and others. Just three months later, Astria raised another $12.5 million in funding, led by dba and Placeholder VC, with participation from Hasu and others.
With the maturity of Ethereum Layer 2 networks and the significant reduction in Gas fees, these networks are experiencing robust growth. However, issues such as fees and speed, which can be affected by various factors, can negatively impact user experience. In this context, the importance of transaction sequencing becomes increasingly prominent, emerging as a key factor in resolving transaction bottlenecks and optimizing user experience.
What is Astria?
Astria is developing a decentralized shared sequencer network aimed at providing Rollups with rapid finality, censorship resistance, composability, and decentralization.
Currently, running a centralized sequencer on L2 is more convenient, cheaper, and easier for users, so mainstream L2s are managed by their own teams. Although L2 users can directly submit transactions to L1 to bypass the sequencer, users must pay L1 transaction Gas fees, and transactions may take longer to finalize.
The sequencer controls the order of transactions and theoretically has the power to exclude user transactions. The sequencer can also extract MEV from the transaction batch. If there is only one sequencer, the risk of centralization increases.
Therefore, a decentralized shared sequencer still holds significance.
How Astria Operates
Astria’s decentralized sequencer comprises multiple sequencer nodes that can sequence Rollup transactions. In Astria’s operating model, users submit transactions to Rollups, which automatically enter their respective Rollup node mempools.
The composer collects these transactions (txns) and sends them to the sequencer. Finally, the sequencer compiles the transactions into a shared block and sends a pre-confirmation to the user.
Current sequencers are implemented for specific Rollups. Astria, however, batch processes blocks for multiple Rollups. Through data compression, it can save more costs when publishing data to L1. The decentralized shared sequencer network will incentivize participants from multiple Rollup ecosystems to act as validators on the network.
Astria Stack
Astria’s main components consist of five parts: the composer, sequencer layer, relayer, DA, and conductor.
Composer
Technically skilled professionals might directly utilize the sequencer layer for better transaction sequencing, but for most ordinary users, this would increase difficulty. Direct interaction with the sequencer layer requires users to hold sequencer tokens and maintain a sequencer wallet, which negatively impacts user experience.
Astria provides the composer to abstract this complexity. The composer acts like a Gas station, covering the sequencing cost of user transactions. The composer also provides an unordered guarantee, bundling transactions in the order they are received.
Sequencer Layer
Astria’s sequencer layer uses CometBFT as its consensus algorithm. Chains supporting CometBFT can support IBC (Inter-Blockchain Communication), meaning it can cross-chain with many other chains.
Astria’s unique feature is that the transactions it includes are not executed (delayed sequencing) but assigned to another execution engine, the Rollup. Sequencer nodes can choose to act as “validators,” actively participating in new block production and finalization.
Astria’s application logic for sequencers allows three main functions:
- Sequencing Rollup data
- Value transfer
- Validator set changes
Relayer
The relayer’s function is to fetch validated blocks from the sequencer and pass them to the DA layer. Since the sequencer’s block time is faster than the DA’s, the relayer first batches ordered data from multiple sequencer blocks, then compresses it before submitting it to the DA.
Individual sequencer blocks can also be picked up by the conductor before the relayer submits them to the DA. This enables improved user experience with rapid finality, acting as a soft commitment for the execution layer. The data sets sent by the relayer to the DA layer serve as the source of truth and are ultimately extracted from the DA for final commitment in the Rollup.
DA
Astria uses Celestia as its data availability layer, the final destination for all data sequenced by the sequencer network. Once data is written to Celestia, the transaction order is considered final. When new Rollup nodes start, all data will be extracted from here.
Conductor
The conductor can be seen as the consensus implementation of the Rollup full node, similar to the operation node in the OP Stack. The conductor corresponds to the execution engine, forming a complete Rollup node. Its role is to connect the sequencer and DA layers to the Rollup execution layer by extracting relevant Rollup data from each conductor block and forwarding it to the execution layer.
For each sequencer block, it extracts the required Rollup data, then verifies the batch of Rollup data. Once verification is complete, it converts it into a list of transactions and passes it to the execution engine.
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