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MEV-Boost

Introduction

MEV-Boost is open-source software developed by Flashbots that implements the Proposer-Builder Separation (PBS) architecture for Ethereum. It runs as a "sidecar" (auxiliary software) to the beacon node, allowing validators to obtain high-MEV (Maximal Extractable Value) blocks from specialized block builders through a competitive market, thereby maximizing staking returns while maintaining Ethereum's decentralization.

Since Ethereum's merge to Proof of Stake, approximately 60% of network validators use MEV-Boost, making it an indispensable piece of infrastructure in the Ethereum ecosystem.

Core Architecture

Three-Layer Structure

Validators (Proposers): - Run a beacon node and execution client - Install MEV-Boost software as middleware - Propose blocks at designated slots - Select the highest bid from multiple relays

Relays: - Aggregate blocks from multiple builders - Verify block validity - Protect the interests of builders and proposers - Pass the highest-bidding block to the proposer - Handle payments and data transmission

Builders: - Specialized block-building entities - Optimize transaction ordering to extract MEV - Submit blocks and bids to relays - Compete to win block space

Workflow

  1. Building Phase:
  2. Builders monitor the mempool and private order flow
  3. Build optimized blocks including MEV extraction strategies

  4. Calculate the bid they are willing to pay the proposer

  5. Submission Phase:

  6. Builders submit blocks and bids to one or more relays
  7. Relays verify block validity (without executing)

  8. Relays store block and bid information

  9. Bidding Phase:

  10. The proposer's MEV-Boost queries all connected relays
  11. Each relay returns its highest-bidding block header

  12. The proposer cannot see block contents (blind selection)

  13. Selection Phase:

  14. The proposer selects the highest-bidding block

  15. Sends the signed block header to the corresponding relay

  16. Reveal Phase:

  17. After verifying the signature, the relay provides the full block body to the proposer
  18. The proposer broadcasts the complete block to the network
  19. The builder's payment is included in the block

MEV and PBS

The MEV Problem

Maximal Extractable Value (MEV): - Arbitrage: DEX price difference arbitrage - Liquidations: DeFi protocol liquidation rewards - Sandwich attacks: Inserting transactions before and after a user's transaction - Front-running: Copying profitable transactions

Centralization Risk: - Complex MEV extraction requires specialized technology and resources - Retail validators struggle to compete - May lead to validator centralization - Threatens network decentralization and security

MEV-Boost's Solution

Democratizing MEV Revenue: - All validators can access professionally built blocks - No need to run complex MEV search infrastructure - Retail and large staking pools compete on equal footing - Significantly increases validator revenue (15-30% additional returns)

Maintaining Decentralization: - Lowers the technical barrier for running a validator - Prevents centralization caused by technical advantages - Encourages more people to participate in staking - Enhances network security

Blind Block Building

Why "Blind Selection" Is Needed

Protecting Builders: - If proposers could see block contents - They might steal MEV strategies and build similar blocks themselves - Builders would lose their competitive advantage - They would be unwilling to share high-value blocks

Solution: - Proposers can only see block headers and bid amounts - Block contents are revealed only after the proposer commits - Cryptographic commitments ensure blocks cannot be tampered with - Ensures builders are willing to share optimal blocks

Trust Model

The Role of Relays: - Acts as a trusted intermediary - Verifies that blocks submitted by builders are valid - Ensures proposers receive the promised payment - Prevents malicious behavior

Risks: - Relays may censor certain transactions or builders - Collusion between relays is possible - Multiple independent relays are needed to increase decentralization

Mitigation Measures: - Run multiple independent relays - Open-source relay code for auditability - Community oversight and reputation mechanisms - Future transition to Enshrined PBS to reduce relay dependency

Current Ecosystem

Major Relays

Public Relays: - Flashbots Relay: The largest relay, operated by Flashbots - BloXroute: Provides low-latency, high-performance relay services - Blocknative: Relay focused on real-time mempool data - Eden Network: Relay supporting priority transactions - Aestus: Independently operated relay

Relay Diversity: - Validators can connect to multiple relays simultaneously - Increases bidding competition and revenue - Enhances network resilience - Reduces single-point-of-failure risk

Builder Market

Market Concentration: - Top builders win 95%+ of bid auctions - Builders retain 27%+ profit margins - Positive feedback loop exists: more private order flow -> higher win rate -> more order flow

Major Builders: - Beaver Build - Titan Builder - Flashbots Builder - BuildAI - Other specialized builders

Private Order Flow: - Users/applications send transactions directly to builders - Avoids front-running risk from the public mempool - Builders compete to provide optimal execution - Accounts for a significant portion of winning blocks

Revenue Enhancement

Additional Income

Validator Revenue Composition (Using MEV-Boost): - Consensus layer rewards: Block proposal and attestation rewards - Execution layer rewards: Priority fees (tips) - MEV-Boost payments: Builder bids - Total uplift: Typically increases revenue by 15-30%

Real-World Examples: - Without MEV-Boost: Only base rewards and priority fees - With MEV-Boost: Additional hundreds to thousands of dollars (depending on the block) - High-MEV blocks can pay tens of thousands of dollars

Revenue Optimization

Connecting Multiple Relays: - Increases competition and raises bids - Different relays may have different builders - Some relays perform better during certain periods

Configuration Options: - Set minimum bid thresholds - Select relay preferences - Enable local block building as a fallback

Security and Censorship Issues

OFAC Compliance

Regulatory Pressure: - Some relays comply with OFAC (U.S. Treasury's Office of Foreign Assets Control) sanctions - Censor transactions related to sanctioned addresses - Raises community concerns about censorship resistance

Community Response: - Non-censoring relays have emerged (e.g., Aestus) - Validators can choose to connect to non-censoring relays - Debate over network-layer censorship vs. application-layer compliance

Centralization Risk

Builder Concentration: - A few top builders control most blocks - Private order flow creates entry barriers - May affect transaction inclusion and pricing

Mitigation Measures: - Encourage more builders to participate - Develop open-source builder software - Research decentralized builder protocols

Future Development: Enshrined PBS

Protocol-Level Integration

Goals: - Integrate PBS directly into the Ethereum protocol - Become part of the consensus rules - Reduce dependency on third-party relays

Advantages: - Trust minimization - Stronger censorship resistance guarantees - Protocol-level fairness - Eliminate relays as single points of failure

Challenges: - Design complexity - Backward compatibility - Balancing efficiency and decentralization - Requires thorough research and testing

Inclusion Lists

Vitalik's Proposal: - Proposers can force the inclusion of certain transactions - Prevents builders from completely censoring transactions - Guarantees eventual transaction inclusion - Balances builder power

Installation and Configuration

Basic Setup

Installing MEV-Boost: 

# Download MEV-Boost binary
wget https://github.com/flashbots/mev-boost/releases/download/vX.X.X/mev-boost_X.X.X_linux_amd64.tar.gz
tar -xzf mev-boost_X.X.X_linux_amd64.tar.gz

# Run MEV-Boost
./mev-boost -relay-check \
  -relay https://relay1.example.com \
  -relay https://relay2.example.com

Configuring the Beacon Node: - Add the MEV-Boost endpoint to the beacon node configuration - Typically http://localhost:18550 - The beacon node queries MEV-Boost through this endpoint

Relay Selection

Considerations: - Relay censorship policy - Historical bid performance - Latency and reliability - Reputation and transparency

Example Relay List: - Flashbots: https://boost-relay.flashbots.net - BloXroute Max Profit: https://bloxroute.max-profit.blxrbdn.com - BloXroute Regulated: https://bloxroute.regulated.blxrbdn.com - Aestus: https://mainnet.aestus.live

Monitoring and Tools

Dashboards: - MEV-Boost Dashboard: Real-time monitoring of relays and builders - MEV-Boost Relay Monitor: Relay performance comparison - Relayscan: Relay data analytics

Metrics: - Relay bid distribution - Builder market share - Censorship rate statistics - Validator revenue uplift

  • PBS
  • MEV
  • Flashbots
  • Relay
  • Builder
  • Proposer
  • Blind Block Building
  • OFAC