Validators and sequencers profit from transaction reordering, exposing systemic risks in decentralized networks’ economic design.
Public blockchains face inherent fairness trade-offs in transaction ordering, enabling validators to extract value through practices like frontrunning and sandwiching. This maximal extractable value (MEV) arises because block proposers control transaction sequencing without protocol-level constraints, creating economic distortions.
Current consensus mechanisms prioritize consistency and liveness but fail to address transaction order fairness. MEV extraction, which can exceed $1 billion annually in Ethereum alone, undermines trust by allowing privileged participants to profit from reordering or censoring transactions.
Proposals for transaction order-fairness aim to limit bias, but no solution eliminates MEV entirely. Network asynchrony and validator incentives continue to challenge perfect fairness, forcing blockchains to adopt varying relaxations of the ideal.