What is MEV Supply Chain

MEV (Maximal Extractable Value) is the extra profit someone can make by controlling transaction ordering, inclusion, or exclusion in a block. That “someone” used to be miners. In proof-of-stake Ethereum, it’s now a whole cast of specialized roles, stitched together into what people call the MEV supply chain.

If you want the clean mental model: users create transactions, searchers find profit opportunities, builders assemble optimal blocks, relays coordinate the handoff, and proposers/validators publish the winning block. The entire pipeline exists because competition for ordering is intense and latency matters. Yes, this is what happens when finance meets distributed systems.

Why MEV became a supply chain

Ethereum’s move to proposer-builder separation (PBS) created room for specialization. Instead of every validator trying to build the most profitable block themselves, validators can outsource block building to a competitive market and just propose the best bid they receive.

Flashbots’ MEV-Boost is the widely used middleware that lets validators access that competitive builder market as a PBS implementation for proof-of-stake Ethereum.

That outsourcing brought efficiency, but also new chokepoints: relays, builder concentration, private order flow, and censorship risk. ESMA’s 2025 paper on MEV notes that a major observed drawback of MEV-Boost is centralization at the relay and builder levels, which raises censorship and operational risk concerns.

The key roles

Users and wallets

Users originate transactions. Their biggest MEV-related decision is whether to send transactions to the public mempool (visible to everyone) or via private routing mechanisms that reduce sandwiching and certain kinds of leakage.

Flashbots also built MEV-Share, an open protocol that lets wallets and apps selectively share transaction data with searchers who bid to include it, with configurable redistribution of that bid.

Searchers

Searchers are the opportunity hunters. They monitor markets and mempools for profitable actions like DEX arbitrage, liquidation execution, or backrun bundles. They then submit bundles (ordered transactions) that capture the opportunity.

Searchers compete with each other, and the “winner” is often determined by who can pay the most to get included and who can deliver the most reliable bundle execution.

Builders

Builders are block assembly specialists. They take user transactions (from public mempool and private channels), plus searcher bundles, then construct a full block designed to maximize revenue while keeping the block valid and timely.

A useful detail: builders increasingly benefit from private order flow, meaning transaction streams that never hit the public mempool. Research analyzing Ethereum blocks (Jan 2023 to May 2024) explores how private order flow changes builder bidding dynamics under PBS auctions.

Relays

Relays sit between builders and proposers. They help coordinate block delivery and protect participants against certain networking and denial-of-service issues. Flashbots describes relays as a “doubly-trusted” layer, trusted by builders for fair payload routing and by proposers for block validity and data availability.

This is one of the uncomfortable truths of today’s MEV pipeline: relays are not purely trustless infrastructure.

Proposers (validators)

Validators propose blocks. With MEV-Boost, validators can choose the most profitable block from one or more relays and propose it to Ethereum.

In effect, proposers rent out blockspace to builders via auctions, taking the highest bid (usually expressed as payments or priority fees).

The MEV flow step-by-step

1) Transactions appear

Users send transactions either publicly (mempool) or privately (protect/auction routes, RPC partnerships, OFA-style systems). Public visibility increases the chance of being sandwiched or copied. Private routing reduces that risk but changes transparency and market structure.

2) Searchers build bundles

Searchers craft bundles that exploit price differences or execute profitable strategies. They simulate to ensure the bundle lands cleanly and doesn’t revert.

3) Builders assemble blocks

Builders combine:

• regular user transactions

• private order flow

• searcher bundles
  and then compute the best ordering to maximize total value while staying within gas limits and block validity constraints.

4) Builders bid through relays

Builders submit block bids to relays. Relays forward the best options to proposers, usually with protections against equivocation and payload withholding.

MEV-Boost documentation describes the block proposal process, including validator registration and how block proposals are delivered through the MEV-Boost pipeline.

5) Proposer selects and publishes

The proposer picks the highest-paying valid block and proposes it. The network then attests and finalizes as usual.

Where the supply chain breaks or bends

Private order flow wars

Private order flow can improve user outcomes by reducing certain attacks, but it can also increase builder advantage and reduce transparency. Builders who control more private flow may extract additional profit beyond what they bid in open competition, which can contribute to builder concentration.

Relay centralization risk

Relays are operational bottlenecks. If a relay goes down, blocks may be missed or builders may be unable to deliver bids. If relays censor transactions, that affects inclusion. ESMA explicitly highlights centralization at relay and builder levels as an observed drawback of MEV-Boost.

Censorship and compliance pressures

Even if builders are competitive, they may still apply inclusion filters due to legal risk, sanctions compliance, or business policy. In a supply chain, the censoring party might be the builder, the relay, or the proposer. That makes accountability messy.

What’s new recently

More push toward enshrined PBS

The Ethereum ecosystem has been exploring “enshrined PBS,” meaning moving the PBS auction mechanism into the protocol rather than relying on off-chain relay infrastructure. EIP-7732 is the main proposal describing enshrined proposer-builder separation.

Ethereum Foundation’s Protocol Priorities Update for 2026 explicitly names enshrined PBS as a target alongside blob scaling and censorship resistance, with Glamsterdam targeted for the first half of 2026.

Builder decentralization efforts

Flashbots writings note a December 2024 migration away from centralized builders toward “BuilderNet,” positioning it as a step toward more resilient block building.

MEV redistribution via MEV-Share

MEV-Share has matured into a practical “order flow auction” approach where users, wallets, and apps can selectively share transaction data and control how bids are redistributed.

This is a big shift in narrative: from “MEV is extracted from users” to “some MEV can be internalized or rebated,” at least in certain flows.

SUAVE and unbundling experiments

Flashbots’ SUAVE concept aims to unbundle the mempool and builder role into a specialized system to improve decentralization and privacy of MEV workflows.

Real-world example

Consider a simple DEX trade on a popular pair during volatility.

1. A user submits a swap to the public mempool.

2. A searcher detects a profitable sandwich opportunity or backrun arbitrage.

3. The searcher simulates bundles and sends them to a builder.

4. The builder integrates that bundle into a block, calculates the maximum bid it can pay while still profiting, and submits bids via one or more relays.

5. A validator running MEV-Boost selects the highest bid and proposes the block.

If the user instead routes privately through MEV-Share-style selective disclosure, the searcher may still bid, but the user can influence who sees what and how value is redistributed.

How to evaluate MEV supply chain health

A sane checklist:

• How concentrated are builders and relays?

• How much private order flow exists, and who controls it?

• Are censorship policies visible and consistent?

• What happens under relay outages or network stress?

• Are users offered credible private routing options?

If your answer is “I have no idea,” that’s not uncommon. It’s also the point: the supply chain is powerful precisely because it’s complex.

Skills and certifications

If you’re working around MEV, you’re dealing with protocol mechanics, market microstructure, and a lot of adversarial thinking. A structured learning mix could include an AI certificate for automation and analytics fundamentals, a Blockchain certificate and Crypto certification for on-chain architecture and cryptographic foundations, a broad tech certification for systems knowledge, and a business-facing marketing certification for explaining trust, risks, and product positioning to humans who control budgets.

Conclusion

The MEV supply chain is the industrialization of transaction ordering. Searchers discover value, builders package it, relays coordinate it, and proposers finalize it. MEV-Boost made this pipeline mainstream, but it also introduced centralization and censorship concerns around builders and relays.

Recent momentum is pushing toward more protocol-native designs like enshrined PBS (EIP-7732) and more user-aware order flow mechanisms like MEV-Share. The endgame is not “eliminate MEV.” It’s making MEV less toxic, less centralized, and less like a shadow market that everyone depends on but nobody