How Arbitrum and Optimism Resolve Rollup Disputes
Summary
The article compares how Arbitrum and Optimism handle challenges to potentially invalid transactions in optimistic rollups. Optimism re-executes a disputed transaction through the EVM in a single round. Arbitrum uses recursive bisection to narrow the disagreement offchain, then asks the EVM to verify a single step. The article presents this as a tradeoff: Optimism can resolve individual disputes faster, while Arbitrum can reduce onchain gas use by verifying less computation and checkpointing less often.
It argues that dispute rules also shape ordinary operation. Because Optimism must be able to verify a whole transaction on Ethereum, transactions must fit within Ethereum’s gas limit; Arbitrum can handle larger computations by splitting verification into steps. The author also describes how Arbitrum’s pipelining lets transaction processing continue while a challenge is unresolved, reducing the potential for repeated disputes to halt progress. These comparisons are qualitative and reflect the article’s account of the protocols at the time. The author discloses an investment in Offchain Labs, and the piece does not provide independent performance measurements.
Key ideas
- Optimism verifies a disputed transaction by running it through the EVM in one round.
- Arbitrum uses recursive bisection to isolate a disputed step for onchain verification.
- Arbitrum’s stepwise dispute design can reduce onchain gas costs and allow less frequent state checkpoints.
- Optimism’s verification approach constrains transactions to what Ethereum can execute within its gas limit.
- Arbitrum’s pipelining can allow processing to continue while disputes remain unresolved.
Tags
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.