With Ethereum’s merge most likely to happen in mid-September 2022, there has been a lively debate about the scaling solutions that are best suited for this task, with the two main contenders being Optimistic Rollup and ZK-Rollup.

Optimistic rollups are a Layer 2 protocol designed to increase the speed of transactions and lower the cost of gas fees on Ethereum’s blockchain. It works by reducing the computational requirement on Ethereum’s chain via processing transactions off-chain, which offers significant improvements in processing speeds.

Optimistic rollups are labelled as ‘optimistic’ due to its assumption that all transactions within a rollup are valid, thereby skipping publishing validity proofs for each transaction. In contrast with sidechain solutions, optimistic rollups still use the primary Ethereum chain for consensus and security.

Optimistic rollups are expected to have roughly 100x more throughput than layer 1 on Ethereum. If chosen, it will go a long way toward relieving some of the congestion Ethereum is currently experiencing.

However, the founder of Ethereum, Vitalik Buterin, has recently come out in favour of ZK-Rollups, citing its faster transaction protocols and cryptographic validity proofs over Optimistic Rollups, and that in the long run, ZK-Rollup will eventually beat Optimistic Rollup.