What is Sequencer?

As part of the Optimistic Rollup (OR) Layer-2 scaling solution proposed for the Ethereum network, sequencers — or aggregators — process transactions off-chain before sending them on-chain to be finalized. While sequencers are financially rewarded for their role in OR models, they must put up a bond — known as a fraud proof — as collateral to disincentivize malicious action. Executed at scale, this methodology could save capital and offer a boon to Ethereum throughput capacity.