Rome: The Rise of Remus

A few months ago, we shared our views on Rome Protocol: The Shared Sequencer using Solana. The idea resonated strongly with the community, and we are excited to share our latest updates.

As we discussed, rollups benefit from the low latency, high throughput, and existing economic security of Solana when they use Rome. Using Solana as a shared sequencer also allows for increased interoperability and access to liquidity across different chains. It allows rollups to focus on enabling applications instead of worrying about cross-chain interoperability infrastructure.

Rome is built for rollups, RaaS providers, app chains, searchers, bundlers, Ethereum developers, and Solana developers. In this blog post, we share how an OP Stack rollup integrates with Rome. We introduce Rhea and Remus, which enable core functionality of Rome. The integration uses Solana as the state machine and data availability (a.k.a. data publication) layer.

Ethereum developers can use technologies they are already familiar with, such as OP Stack, without any changes, while using Solana for execution and maintaining state. There is no change in the user experience for rollup users; they can continue to use rollups as usual via ordinary RPCs.

Searchers, bundlers, and aggregators can interact with applications using atomic execution of transactions, thereby increasing interoperability and improving the efficiency of markets across L2s. This enables use cases for atomic arbitrage, bridging, liquidity, aggregation, and RWAs.

This blog post illustrates how Rome enables atomic execution of cross-rollup transactions for OP Stack rollups. We will be opening up more opportunities for the developer and rollup communities to engage with Rome soon. Stay tuned for more updates on community engagement and the upcoming Devnet launch.

Rhea API enables Solana to be used as a shared sequencer that executes rollup transactions, maintains state, and publishes transactions. By using the Rhea API, transactions pending in the rollup's OP Geth mempool are processed, packaged for Solana, and submitted to Solana. The corresponding rollup program on Solana then executes these transactions. After this, a block is created, and the rollup state is advanced.

Transactions are picked up from rollups in a first come, first serve order and submitted to Solana. The execution and state on Solana is what determines the order of transactions, which is ultimately determined by the Solana leader node.

The Remus API enables atomic execution of cross-rollup transactions. Searchers and bundlers can use Remus to construct an atomic transaction bundle that spans across multiple rollups. This Solana transaction is then executed atomically, updating the states of involved rollups at the same time. The diagram below illustrates how bundlers use Remus to compose atomic transactions and submit them to Solana.

Cross-rollup atomic transactions enable use cases for atomic arbitrage, bridging, liquidity, aggregation, and RWAs. Low latency, high throughput, and fast confirmations benefit users such as hedge fund traders.

The example below shows how Remus is used for cross-rollup arbitrage. A searcher identifies a price discrepancy for an asset (for example, ROME) across rollups. It creates two orders: a buy order on Rollup 1, where the price is lower, and a sell order on Rollup 2, where the price is higher. Remus is then used to atomically compose, bundle, and execute these orders on Solana, reducing the risk of one of the orders being reverted.

Rhea enables fair and blind sequencing of rollup transactions, all transactions are treated the same and processed first come first serve.

Remus provides cross rollup atomic composability as a premium transaction service allowing expansion of ecosystem services. The table below highlights differences between the two.