MEV Relay Network

An MEV Relay Network is a decentralized network of servers, or relays, that receive blocks from specialized builders and forward them to validators. Its primary function is to act as a neutral intermediary, preventing validators from viewing the contents of a block before committing to propose it. This separation is crucial because it prevents validators from engaging in time-bandit attacks, where they could discard a received block to steal its MEV and re-mine it themselves. By providing this cryptographic commitment, relays enable a competitive market for block building without compromising chain security.

The architecture of a relay network directly addresses the censorship and centralization risks inherent in MEV extraction. Without relays, validators might be incentivized to only accept blocks from a single, dominant builder, creating a central point of failure. Relays standardize the block submission process, allowing multiple builders to compete on a level playing field. They typically implement a first-price auction or similar mechanism, where builders submit their most profitable block along with a fee, and the relay passes the highest-value, valid block to the validator. This process is often called proposer-builder separation (PBS) in practice.

Key technical components of a relay include the public mempool for transaction submission, a builder API for receiving sealed block bids, and a validator API for delivering the winning header. Reputable relays also provide attestations or proofs of block availability, ensuring validators that the full block body can be retrieved. Prominent examples include the Flashbots Relay, which pioneered the concept on Ethereum, and other networks like BloXroute, Eden Network, and Manifold. These networks are critical public goods for maintaining liveness and fairness in modern blockchain ecosystems.

The operation of relay networks raises important considerations around trust assumptions and relay neutrality. While relays do not have the power to censor transactions themselves, their operators could theoretically filter which builders are allowed to participate. Therefore, the health of the ecosystem depends on relay diversity, where validators connect to multiple relays to avoid reliance on any single operator. Furthermore, ongoing protocol-level developments, such as enshrined PBS and suave, aim to incorporate the relay's functionality directly into the consensus layer, reducing reliance on this extra-protocol infrastructure over time.

An MEV relay network is a specialized communication protocol and marketplace that connects searchers (who identify profitable transaction opportunities) and block builders (who construct optimized blocks) with validators (who propose and attest to blocks). Its primary function is to receive blocks from builders and forward them to validators, often in exchange for a portion of the MEV profits. By acting as a trusted intermediary, the relay network ensures validators receive the most profitable block without having to inspect or construct it themselves, a process known as outsourced block production. This separation of roles is a cornerstone of proposer-builder separation (PBS) architectures.

The core workflow begins when a searcher submits a bundle of transactions—a pre-ordered set often including a backrun, frontrun, or arbitrage—to a builder via the relay. The builder aggregates these bundles and other pending transactions from the public mempool to construct a candidate block, aiming to maximize the total value for the validator (the block reward plus any priority fees). The builder then submits this complete block, along with a bid (a commitment to pay the validator a certain amount), to the relay network. The relay validates the block's correctness and propagates the highest-bidding block to connected validators.

Relay networks enhance network integrity by implementing critical safeguards. They perform simulation to ensure the proposed block is valid and will be accepted by the network, preventing validators from proposing invalid blocks and being slashed. Many relays also enforce censorship resistance lists, committing to not exclude transactions based on origin, and provide data transparency by publishing received blocks and bids. Prominent examples include the Flashbots Relay, which pioneered the model on Ethereum, and relays operated by entities like BloXroute and Blocknative. These networks are essential for democratizing access to MEV and reducing its negative externalities, such as network congestion.

The MEV Relay Network emerged as a critical infrastructure layer to mitigate the risks of frontrunning and transaction censorship inherent in decentralized block production. It functions as a trusted, neutral communication channel where validators (block proposers) can receive execution payloads—complete, pre-built blocks—from specialized builders, without seeing the transactions inside. This separation, enforced through cryptographic commitments, prevents validators from stealing profitable transaction bundles or reordering them for personal gain, a practice known as proposer-builder separation (PBS). The relay's role is to receive these blinded blocks from builders, run basic validity checks, and forward the most profitable one to the current validator.

The initial implementation, often called outsourced PBS, relied on a network of off-chain, permissioned relays. While effective, this model introduced new centralization risks and trust assumptions, as relay operators could theoretically censor builders or collude. The evolution towards Enshrined PBS seeks to eliminate this trusted intermediary by baking the core auction mechanics directly into the blockchain's consensus protocol. In this native model, the protocol itself would facilitate a credible commitment between builders and proposers, using in-protocol slashing conditions and verifiable delay functions (VDFs) to ensure fairness and censorship resistance without relying on a third-party network.

The path from relay networks to enshrined PBS represents a fundamental shift in how block space is allocated and value is distributed. It moves critical economic logic from an off-chain, social layer to an on-chain, cryptographic guarantee. This transition aims to achieve the original goals of PBS—reducing validator centralization, democratizing access to MEV, and improving network security—while removing the fragility and trust associated with external infrastructure. The end state is a more robust, transparent, and decentralized mechanism for block production, integral to the long-term health of proof-of-stake networks.