What is MEV-Boost?
- Author
- CRYPTO PORT Editorial
- Published
- Updated
- Reading time
- 6 min
In short
MEV-Boost is software that lets an Ethereum validator outsource block construction to external builders and pick the most profitable result. It is not part of the protocol itself but an optional add-on. The validator signs without seeing the contents, so it depends on trusting an intermediary called a relay.
Key points
- Outsources block construction to external builders
- An optional external tool, not part of the protocol
- The validator signs a header without seeing the body
- Relies on trusting an intermediary called a relay
Definition
Middleware that lets an Ethereum validator receive blocks built by external builders through a relay and propose the most profitable one.
A validator building its own block can do little more than pull transactions from the mempool and order them. Specialist builders, by contrast, construct orderings that capture arbitrage and liquidations and extract more value. MEV-Boost passes that value to the validator in return for outsourcing construction.
The flow works like this: builders send blocks to a relay, which shows the validator only a header and a bid, keeping the body hidden. The validator signs the highest bid, and only then does the relay reveal the contents. Hiding the body first is what stops validators from stealing the builder's transactions.
That puts the relay in the position of guaranteeing both that the body matches the bid and that it will actually be revealed after signing. A misbehaving relay can leave a validator proposing an empty block, and missed blocks from failed reveals have been reported in practice.
Watch out for
- · If a relay filters certain transactions, those transactions do not make it into that block
- · As a validator, a relay failure can cost you a missed proposal and its reward
- · Users' transactions remain subject to reordering and can fill at a worse price