Relays are the bottleneck. Validators outsource block building to specialized builders, but they must connect through a relay. This relay is a centralized server that receives bundles, filters for validity, and passes the highest-bidder to the validator. The validator's role is reduced to signing the winning header.
the-ethereum-roadmap-merge-surge-verge
Blog
MEV Relays Are Ethereum’s Soft Gatekeepers
Proposer-Builder Separation (PBS) created a new power center. MEV relays now decide which blocks get built, creating subtle but critical centralization risks that threaten Ethereum's credibly neutral foundation. This is the Surge's core challenge.
introduction
THE GATEKEEPERS
The Illusion of Decentralization
MEV relays are the centralized, permissioned gatekeepers that control access to Ethereum's decentralized block production.
The relay cartel is real. Over 90% of post-Merge blocks are built by just three entities: Flashbots, BloXroute, and Blocknative. This concentration creates a single point of censorship and failure. A relay can blacklist transactions or entire protocols, acting as a de facto regulator.
Proposer-Builder Separation (PBS) formalizes this. In-protocol PBS, a core Ethereum upgrade, will codify this separation of roles. The goal is to mitigate validator centralization, but it institutionalizes the relay's gatekeeping power within the protocol's economic design.
Evidence: The 'top 3' relays consistently produce over 90% of Ethereum blocks. A single relay, Flashbots, often commands >50% market share. This is not a competitive market; it is an oligopoly with soft power over transaction inclusion.
key-trends
MEV RELAYS ARE ETHEREUM'S SOFT GATEKEEPERS
The Relay Power Triad
Relays are the critical, centralized infrastructure that validators rely on to build and propose blocks. They control transaction ordering, censorship, and the flow of billions in MEV.
01
The Problem: Centralized Censorship
Relays are the primary vector for OFAC compliance, filtering transactions from sanctioned addresses. This creates a soft fork, undermining Ethereum's neutrality.
- ~80% of post-merge blocks are OFAC-compliant.
- Creates a two-tiered system where some transactions are "unbundled" and delayed.
~80%
OFAC Blocks
3
Dominant Relays
02
The Solution: Permissionless Relay Design
Protocols like Flashbots SUAVE and EigenLayer's EigenDA aim to decentralize the relay layer by separating block building from proposing.
- Builders compete in a permissionless auction.
- Validators receive the most profitable, censorship-resistant block.
- Breaks the oligopoly of bloXroute, Titan, and Manifold.
0
Trusted Operators
100%
Uptime Goal
03
The Reality: Latency Is King
The relay market is a winner-take-most game dictated by sub-second latency. Fastest propagation wins the MEV.
- Top relays operate with ~100ms network latency to validators.
- This creates natural centralization pressure, as speed requires global, optimized infrastructure.
- Solutions must solve speed without re-centralizing.
~100ms
Propagation Latency
$1B+
Annual MEV Flow
deep-dive
THE POWER SHIFT
From Neutral Carrier to Active Arbiter
MEV relays have evolved from simple message-passers into the de facto gatekeepers of Ethereum block production, wielding outsized influence over transaction inclusion and network latency.
Relays control block space access. Builders submit blocks to relays, which then forward them to proposers. This creates a centralized filtering layer where relay operators decide which blocks are even seen by validators, directly impacting censorship resistance and MEV extraction efficiency.
The relay market is an oligopoly. Flashbots' mev-boost relay dominates with >90% market share, creating systemic risk. Competitors like BloXroute and Agnostic exist but face significant adoption hurdles due to network effects and trust assumptions in the relay-proposer-builder separation model.
Relay performance dictates network latency. A relay's geographic location and infrastructure quality determine propagation speed. This creates a latency arbitrage game where builders compete on milliseconds, centralizing block building around low-latency, high-capital entities.
Evidence: In Q1 2024, over 99% of Ethereum blocks were built via mev-boost, with the top three relays (Flashbots, BloXroute, Agnostic) processing the vast majority. A relay outage would immediately cripple Ethereum's block production.
ETHEREUM CONSENSUS LAYER
Relay Market Share & Censorship Metrics
Comparative analysis of dominant MEV-Boost relays by market share, censorship policies, and operational transparency.
| Metric / Policy | Flashbots Relay | BloXroute Max Profit | Ultrasound Relay | Agnostic Relay |
|---|---|---|---|---|
Market Share (Last 30d) | 38.2% | 21.5% | 16.8% | 8.1% |
Censorship Compliance | ||||
OFAC Sanctions Filter | ||||
Public Inclusion List | ||||
Avg. Block Value Extracted | 0.32 ETH | 0.35 ETH | 0.29 ETH | 0.27 ETH |
Proposer Payment Model | Pay for Inclusion | Pay for Performance | Pay for Inclusion | Pay for Performance |
Open Source Client | ||||
Avg. Relay Latency | < 500ms | < 300ms | < 700ms | < 450ms |
counter-argument
THE GATEKEEPERS
The Builder's Defense: Efficiency Isn't Tyranny
MEV relays are the de facto arbiters of block production, centralizing power not through malice but through the relentless pursuit of extractable value.
Relays are the gatekeepers. They are the mandatory routing layer between proposers and builders, deciding which builder's block gets forwarded. This creates a centralized point of censorship and failure, as seen in OFAC compliance debates.
Efficiency creates centralization. The competitive search for Maximal Extractable Value (MEV) naturally consolidates block building into a few specialized entities like Flashbots and bloXroute. Their infrastructure and data advantages are insurmountable for casual builders.
The defense is economic necessity. A relay that censors or performs poorly loses proposer trust and market share. The proposer-builder separation (PBS) framework formalizes this, attempting to quarantine centralization to the builder layer while keeping validator decentralization intact.
Evidence: Post-Merge, over 90% of Ethereum blocks are built by just five entities, with Flashbots' mev-boost relay dominating. This isn't a conspiracy; it's the market's solution for optimizing block space value.
risk-analysis
MEV RELAYS ARE ETHEREUM'S SOFT GATEKEEPERS
The Soft Gatekeeper Risk Matrix
MEV relays are the unregulated, centralized arbiters of block production, creating systemic risks for Ethereum's decentralization and censorship resistance.
01
The Censorship Vector
Relays like Flashbots Protect and bloXroute can filter transactions based on OFAC compliance, acting as soft gatekeepers. This creates a two-tiered system where sanctioned addresses are excluded from the dominant block-building path.
- Risk: ~80%+ of blocks are built via OFAC-compliant relays.
- Impact: Undermines Ethereum's credible neutrality and creates legal liability for validators.
80%+
OFAC Blocks
1
Tiered System
02
The Centralization Trap
The relay market is dominated by a few entities, creating a single point of failure. Validators are economically incentivized to use the most profitable relay, leading to herd behavior and reduced network resilience.
- Risk: Top 3 relays control >90% of relayed blocks.
- Consequence: A relay outage or exploit could stall a significant portion of Ethereum's block production.
>90%
Market Share
Single
Point of Failure
03
The Builder Monopoly Problem
Relays are gateways to a small cartel of professional block builders (e.g., builder0x69, beaverbuild). This centralizes the actual construction of blocks, limiting competition and enabling sophisticated MEV extraction that disadvantages retail users.
- Risk: Top 5 builders construct ~80% of Ethereum blocks.
- Result: MEV profits are captured by a few, while transaction ordering fairness degrades.
~80%
Builder Share
Cartel
Risk
04
Solution: PBS & SUAVE
Proposer-Builder Separation (PBS) is the architectural fix, but its full implementation is delayed. In the interim, SUAVE aims to decentralize the mempool and block building by creating a competitive marketplace for preference expression.
- Goal: Break the relay/builder cartel by commoditizing block space.
- Vision: A unified auction for cross-chain MEV, reducing the gatekeeper role of today's relays.
PBS
Architecture
SUAVE
Interim Fix
05
Solution: Permissionless Relays
Networks like Eden and Aestus are launching as permissionless, non-censoring relays. Their growth is critical for providing validators with credible, profitable alternatives to the dominant, compliant options.
- Metric: Their combined market share is the key health indicator for decentralization.
- Requirement: Validators must actively diversify their relay endpoints to reduce systemic risk.
Eden
Permissionless
Aestus
Non-Censoring
06
Solution: Encrypted Mempools
Protocols like Shutter and Fairblock encrypt transactions until they are included in a block, neutralizing frontrunning and reducing the value extractable by centralized builders. This attacks the economic incentive for the current relay cartel.
- Mechanism: Threshold Encryption via Distributed Key Generation (DKG).
- Outcome: Levels the playing field, making simple, decentralized builders viable again.
Shutter
Encryption
Fairblock
Fair Ordering
future-outlook
THE SOFT POWER
The Surge's Real Test: Dissolving the Gate
MEV relays are the unregulated gatekeepers that will define Ethereum's post-Surge censorship resistance and economic efficiency.
Relays control block production. Builders submit blocks to relays, which select winners and forward them to validators. This makes relays the de facto censorship filter for the entire network.
PBS separates proposer from builder. Proposer-Builder Separation (PBS) outsources block building to specialized actors like Flashbots, but the relay layer is a centralization bottleneck.
The relay cartel is real. A few dominant relays like Flashbots, BloXroute, and Manifold process most blocks. This creates systemic risk and coordination points for OFAC compliance.
Enshrined PBS is the endgame. Ethereum's roadmap includes enshrined PBS (ePBS) to protocolize this function, dissolving the trusted relay layer and returning gatekeeping power to the validator set.
takeaways
MEV RELAYS ARE ETHERIUM'S SOFT GATEKEEPERS
TL;DR for Protocol Architects
Relays are not neutral infrastructure; they are critical, centralized choke points that define block production and extract billions in value.
01
The Centralized Censor
The Flashbots Relay and its competitors control which blocks reach proposers. They are centralized, trusted entities that can censor transactions or entire protocols, making them de facto gatekeepers of Ethereum's state.
- Single Point of Failure: A relay outage can halt block production for major builders.
- Regulatory Attack Vector: A compliant relay could filter sanctioned addresses, undermining neutrality.
- ~90% Dominance: Flashbots historically commanded this share of MEV-boost blocks.
~90%
Historical Share
1
Critical Failure Point
02
The Builder Cartel
Top builders like Jito Labs, Titan, and beaverbuild rely on relays. This creates an oligopoly where a handful of entities control block template creation and the flow of MEV.
- Vertical Integration: Builders often run their own relays, consolidating control.
- Information Asymmetry: Relays see all bids, creating potential for front-running or preferential treatment.
- $1B+ Extracted: Estimated annual MEV value flowing through this cartel.
$1B+
Annual MEV Flow
Oligopoly
Market Structure
03
The Latency Arms Race
Block building is a sub-second auction. Relays are the timing layer, where ~100ms advantages determine winners. This forces extreme centralization in low-latency, high-cost data centers.
- Geographic Centralization: Builders cluster near relays in Virginia and Frankfurt for speed.
- Barrier to Entry: Requires millions in infrastructure, stifling decentralization.
- ~500ms Window: The total time from bid submission to block proposal.
~100ms
Winning Edge
~500ms
Total Auction Window
04
Solution: SUAVE
Flashbots' SUAVE (Single Unifying Auction for Value Expression) aims to dismantle the relay gatekeeper role. It proposes a decentralized, specialized mempool and blockchain for preference expression.
- Decentralized Sequencing: Moves auction logic to a neutral chain, not a trusted server.
- Intents & Privacy: Users express outcomes, not transactions, reducing front-running.
- New Design Space: Enables cross-domain MEV and intent-based bridges like UniswapX.
Decentralized
New Architecture
Intents
Core Primitive
05
Solution: PBS-Enshrined
The endgame is Enshrined Proposer-Builder Separation (PBS), baked into the Ethereum protocol. This would eliminate the need for trusted relays by moving the auction on-chain.
- Trustless Auctions: Builders commit bids via cryptography, not to a central party.
- Censorship Resistance: Protocol-level rules prevent transaction filtering.
- Long-Term Horizon: Likely a post-Verge (Verkle Trees) upgrade, years away.
Protocol-Level
Integration
Trustless
End State
06
Immediate Mitigations
Architects can't wait for SUAVE or enshrined PBS. Tactics now include multiple relay redundancy, monitoring for censorship, and designing for MEV resistance.
- Diversify Relays: Use Agnostic Gnosis, Ultra Sound, BloxRoute alongside Flashbots.
- MEV-Share / MEV-Burn: Protocols like EigenLayer and EIP-1559 attempt to socialize or burn extracted value.
- Fair Ordering: Explore FCFS lanes or encrypted mempools to reduce predatory MEV.
4+
Relays to Use
MEV-Burn
Current Tactic
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