MEV-Boost is an early out-of-protocol iteration of Proposer-Builder Separation (PBS). It was developed by Flashbots and went live on Ethereum after the Merge. It allows validators (proposers) to outsource block building to sophisticated entities (builders) who can build higher value blocks that maximize MEV received. A doubly-trusted entity known as a relay sits between the builder and proposer.
MEV-Boost seeks largely to address two shortcomings of MEV-Geth from proof-of-work Ethereum:
- Client diversity – MEV-Boost is run as a sidecar compatible with any Ethereum client (as opposed to being a fork of Geth).
- Open to many participants – MEV-Boost allows any validator to participate while reducing the trust that needs to be placed in them by using a commit-reveal scheme over blocks. MEV-Geth only worked with a handful of mining pool operators who were trusted to behave honestly.