What is MEV?
Maximal Extractable Value (MEV) is the value that block producers (miners under PoW, validators under PoS) can extract from a block by including, excluding, or reordering transactions in a way that benefits them — beyond standard block rewards and transaction fees. MEV emerges because of the discretion block producers have over transaction ordering, and is most pronounced in DeFi where atomic arbitrage and liquidation opportunities create extractable rents.
Common MEV strategies
- Arbitrage: price differences across DEXs captured by atomic same-block swaps.
- Liquidations: earning liquidation bonus on undercollateralised lending positions (Aave, Compound).
- Sandwich attacks: placing a buy before a victim’s swap and a sell after, profiting from induced slippage.
- Frontrunning: seeing pending transactions in the mempool and racing ahead with a higher gas bid.
- Backrunning: placing a transaction immediately after a target to capture state changes (often benign, e.g., arbitrage normalising post-trade prices).
MEV mitigation — Flashbots and proposer-builder separation (PBS)
Flashbots and MEV-Boost introduced private orderflow channels where users submit bundles to block builders without exposing them to public mempool frontrunning. Ethereum’s Proposer-Builder Separation roadmap formalises this: validators delegate block-building to specialised builders via competitive auctions, distributing MEV more efficiently and reducing centralisation pressure.
MEV as a compliance topic
MEV stopped being only a protocol curiosity when regulators began treating ordering games as market conduct. Sandwich attacks against users resemble front-running; validator-level reordering raises fair-access questions; and for any Turkish CASP or trading venue, surveillance expectations extend to detecting abusive patterns in execution quality. Contract and disclosure consequences follow: routing policies (private mempools, MEV-protected RPCs) belong in product documentation; execution-quality claims must match the routing reality; and institutional clients increasingly ask for MEV-protection commitments in service agreements. Teams building on-chain execution products should document their ordering policies the way brokers document best execution — same instinct, new substrate.