Centralized relay networks are the critical failure point. MEV-Boost outsources block building to a permissioned set of relays, creating a single point of censorship and failure. This architecture inverts Ethereum's security model by concentrating power.
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Why Centralized Relay Networks in MEV-Boost Compound the Problem
MEV-Boost was a necessary fix for post-Merge validator economics, but its reliance on a handful of dominant relays has created new, critical chokepoints. This analysis breaks down how BloXroute, Agnostic, and others centralize block production, why this matters for Lido and EigenLayer, and the systemic risks it introduces.
introduction
THE CONCENTRATION
Introduction
MEV-Boost's centralized relay architecture centralizes block production power, creating a systemic risk that undermines Ethereum's decentralization.
The relay oligopoly controls transaction ordering. Dominant relays like BloXroute and Flashbots decide which transactions enter blocks, replicating the centralized sequencer problem seen in early Optimism and Arbitrum rollups.
Evidence: Over 90% of post-Merge Ethereum blocks use MEV-Boost, with the top three relays consistently controlling the majority of this flow. This creates a latent regulatory attack surface.
key-trends
MEV-BOOST RELAY RISKS
The Centralization Landscape: Key Trends
MEV-Boost's reliance on a handful of centralized relay operators creates systemic fragility and extracts value from the base layer.
01
The Single Point of Failure
The dominance of 3-4 major relays (e.g., Flashbots, bloXroute, Agnostic) creates a critical chokepoint. Their servers are the sole conduit for ~90% of Ethereum blocks, making censorship and transaction blacklisting trivial. This architecture reintroduces the trusted intermediary that decentralization was meant to eliminate.
~90%
Block Share
3-4
Key Entities
02
The Opaque Tax
Relays are black boxes that capture MEV value. They perform off-chain auction matching and bundle construction, extracting fees and information rents before builders ever see the transaction flow. This creates a multi-billion dollar market where the infrastructure layer, not the protocol or users, captures the surplus.
$1B+
Annual MEV
Opaque
Fee Structure
03
The Builder Monopoly Feedback Loop
Centralized relays favor large, capital-rich builders (e.g., beaverbuild, Rsync). They offer private orderflows and guaranteed inclusion, creating a feedback loop where top builders win more blocks, attracting more exclusive orderflow. This entrenches builder centralization, reducing competition and innovation.
>50%
Top 3 Builders
Private
Orderflow
04
The Protocol Sovereignty Erosion
MEV-Boost outsources Ethereum's core consensus function—block production—to an off-chain, permissioned system. This erodes protocol-level guarantees of credibly neutral inclusion. The network's liveness and censorship resistance become dependent on the goodwill and legal jurisdiction of a few corporate entities, not cryptographic proof.
Off-Chain
Consensus
Jurisdictional
Risk
CENTRALIZATION RISK ANALYSIS
Relay Market Share & Influence (Last 30 Days)
Quantifying the dominance and influence of centralized relay networks in the MEV-Boost ecosystem, highlighting systemic risks.
| Metric / Feature | Top 3 Relays (Aggregate) | All Other Relays (Aggregate) | Ideal Decentralized State |
|---|---|---|---|
Market Share of Proposed Blocks |
| < 15% | Distributed (< 33% per entity) |
Avg. Censorship Compliance (OFAC) |
| < 40% | 0% (Protocol-Neutral) |
Avg. Time to Inclusion | < 1.0 sec | 1.5 - 3.0 sec | < 1.5 sec |
Proposer Fee Extracted (30d) |
| < 800 ETH | Minimized via Competition |
Single Point of Failure Risk | |||
Cross-Relay Builder Cartel Linkage | |||
Supports MEV-Boost++ / PBS Roadmap |
deep-dive
THE CONCENTRATION
How Centralized Relays Compound the Problem
MEV-Boost's reliance on a few centralized relay operators creates systemic risks that undermine the very decentralization it was meant to preserve.
Relays become centralized choke points. MEV-Boost outsources block building to a competitive market, but block proposal flows through a handful of trusted relays like BloXroute and Flashbots. This creates a single point of failure and censorship.
The relay cartel controls information. Builders submit blocks to all relays, but a dominant relay like BloXroute can selectively withhold the most profitable blocks. This distorts the builder market and creates a principal-agent problem for validators.
Relay trust is a regressive assumption. The system assumes relays are honest and will not censor transactions. This reintroduces the exact trusted third-party risk that proof-of-work and proof-of-stake were designed to eliminate.
Evidence: Post-Merge, over 90% of Ethereum blocks used MEV-Boost, with just three relays consistently controlling the majority of relayed blocks. This concentration creates a tangible liveness risk for the network.
counter-argument
THE MARKET FAILURE
The Steelman: Aren't Relays Just Efficient Markets?
Centralized relay networks in MEV-Boost create a cartel that externalizes risk and centralizes trust, undermining the very decentralization they were meant to preserve.
Relays centralize trust. The MEV-Boost auction model outsources block building to a permissioned set of relay operators. This creates a single point of censorship and failure, contradicting Ethereum's credibly neutral base layer.
Relays externalize systemic risk. Builders bid for blockspace without posting capital, creating a moral hazard. This led to the $20M EigenLayer slashing event, where relay validators bore the loss for builder misbehavior.
The market is not efficient. Dominant relays like BloXroute and Ultra Sound control the flow of most MEV-Boost blocks. This oligopoly structure extracts rent and creates coordination vulnerabilities, as seen in OFAC compliance pressures.
Evidence: Over 90% of post-Merge Ethereum blocks use MEV-Boost, with the top three relays consistently controlling more than two-thirds of the relayed block market share, per Flashbots data.
risk-analysis
SYSTEMIC RISK
The Bear Case: Cascading Failure Scenarios
MEV-Boost's reliance on a handful of centralized relay operators creates single points of failure that can propagate across the Ethereum network.
01
The Single Point of Censorship
Relays are the gatekeepers for block production, creating a centralized chokepoint for OFAC compliance. A relay failure or malicious censorship can halt a significant portion of the chain's blockspace.
- ~90% of post-merge blocks are built via MEV-Boost.
- ~3-5 major relays dominate the market share.
- A coordinated takedown or regulatory action against a major relay could cause immediate, measurable chain-level censorship.
~90%
Blocks Affected
3-5
Critical Entities
02
The Data Availability Black Box
Builders submit only block headers to relays, withholding the full block body. This creates a critical dependency where validators must trust the relay to deliver the payload in time.
- If a relay fails to deliver the body, the validator's block proposal fails, leading to missed slots and lost revenue.
- This failure mode is opaque and non-verifiable until the last second, increasing reorg risk.
- Centralized infrastructure like Flashbots Protect and bloxroute become systemic dependencies.
~12s
Critical Window
100%
Blind Trust
03
The Builder-Relay Cartel
Vertical integration between builders (e.g., Titan, beaverbuild) and relays creates anti-competitive markets and hidden centralization. A dominant builder-relay pair can manipulate the auction.
- They can prioritize their own builder's blocks, extracting maximal value.
- They can censor transactions or front-run with impunity.
- This centralizes MEV profits and reduces the economic viability of independent builders, further entrenching the cartel.
>60%
Builder Dominance
Cartel Risk
Market Structure
04
The Liveness-Activity Feedback Loop
Relay liveness is tied to builder activity. A crash in builder profitability (e.g., low MEV, high gas) can cause builders to shut down, reducing relay revenue and incentive to maintain infrastructure.
- This creates a death spiral where lower relay quality reduces block value, further depressing builder activity.
- The system assumes perpetual economic incentive, which fails during bear markets or protocol-level changes (e.g., EIP-1559, PBS).
- Contrast with decentralized alternatives like SUAVE, which decouples these roles.
Death Spiral
Risk Model
Proposer-Builder-Separation
Incomplete
05
The Cross-Chain Contagion Vector
Centralized relay operators (e.g., bloxroute, Blocknative) often service multiple chains. A failure or attack on their core infrastructure can cascade across Ethereum, Polygon, Avalanche, and other supported L2s.
- Shared codebases and operational teams create a common vulnerability.
- This violates the core blockchain tenet of sovereign fault isolation.
- It mirrors the systemic risk seen in CeFi (FTX, Celsius) but in core consensus infrastructure.
Multi-Chain
Failure Domain
CeFi-like Risk
Architecture
06
The Regulatory Kill Switch
A legally compelled relay is a de facto network-level kill switch. Jurisdictional pressure on a US-based entity like Flashbots could force transaction filtering at the consensus layer.
- This is more severe than application-level (e.g., Tornado Cash) censorship.
- Validators would be forced to choose between compliance and chain integrity, potentially causing a contentious hard fork.
- Highlights the need for permissionless, credibly neutral relays and enshrined PBS.
Network-Level
Censorship
Credible Neutrality
Compromised
takeaways
MEV-BOOST'S CENTRALIZATION TRAP
TL;DR for Protocol Architects
MEV-Boost outsources block building to a competitive market but centralizes relay selection, creating systemic risks that undermine the very decentralization it aims to protect.
01
The Censorship Vector
Relays act as mandatory gatekeepers. If a few dominant relays (e.g., Flashbots, BloXroute, Titan) comply with OFAC sanctions, they can censor transactions at the network layer. This creates a single point of failure for Ethereum's credible neutrality.
- >90% of post-Merge blocks have been relayed.
- Censorship is enforced pre-consensus, before validators even see the block.
>90%
Relayed Blocks
3-5
Dominant Relays
02
The Liveness & Extractability Risk
Centralized relay infrastructure is vulnerable to downtime, manipulation, and exclusive order flow (EOF) deals. This harms both chain liveness and user outcomes.
- A relay outage can cause mass reorgs and stalled blocks.
- EOF agreements (like with CowSwap, UniswapX) can route the most valuable MEV to a select few builders, reducing validator revenue and worsening execution for general users.
~0.5 ETH
Avg. MEV/Block
High
Liveness Risk
03
The Protocol-Level Solution: Enshrined Proposer-Builder Separation (PBS)
The only robust fix is to move the relay's trust-minimized functions into the core protocol. Enshrined PBS (ePBS) eliminates the trusted relay intermediary through cryptoeconomic commitments and in-protocol channels.
- Builders commit to blocks on-chain.
- Validators choose the highest-value commitment without a third party.
- Removes censorship capability and centralization points.
0
Trusted Relays
Protocol
Native Guarantees
04
The Interim Fix: Relay Diversity & SUAVE
While ePBS is developed, architects must force relay competition and explore alternative infrastructures like SUAVE. This mitigates, but does not solve, the centralization risk.
- Validators must randomize relay selection or use multiple relays.
- SUAVE aims to decentralize the block building market itself, creating a universal preference environment separate from execution layers.
Multi-Relay
Client Strategy
Universal
SUAVE's Goal
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