One year after Ethereum’s historic transition to proof-of-stake—the Merge—the ecosystem continues to adapt and innovate. A cornerstone of this evolution has been the rise of MEV-Boost and the broader reconfiguration of the Maximal Extractable Value (MEV) supply chain. This article explores the transformations in proposer-builder separation (PBS), relays, block builders, and searchers over the past 12 months, offering data-driven insights into how Ethereum’s post-Merge infrastructure has matured.
Core keywords: Ethereum Merge, MEV-Boost, proposer-builder separation, block builders, MEV supply chain, relays, searchers, decentralization
The Rapid Adoption of MEV-Boost
The Merge marked a pivotal shift in Ethereum’s consensus mechanism, transferring block production from centralized mining pools to a globally distributed set of validators. This transition necessitated a hard reset of MEV infrastructure, dissolving prior miner-searcher relationships and creating an open playing field.
In response to growing concerns about MEV centralization, Vitalik Buterin introduced the concept of proposer-builder separation (PBS) well before the Merge. Without PBS, validators with superior infrastructure or exclusive access to high-value MEV opportunities could gain disproportionate rewards—threatening decentralization and fair participation.
Enter MEV-Boost, developed by Flashbots in collaboration with client teams and the Ethereum Foundation. As a protocol-external implementation of PBS, MEV-Boost required no changes to Ethereum’s core protocol. Instead, it operated as a “sidecar” to consensus layer clients, enabling validators to outsource block construction to specialized builders via a competitive, open market.
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This innovation democratized MEV access, allowing solo stakers—often lacking technical resources—to earn a fair share of MEV revenue. The adoption curve was steep: within one month of the Merge, 50% of validators were using MEV-Boost; by the end of the second month, that number reached 90%.
Data shows that validators using MEV-Boost earned median block rewards on par with those building locally, effectively mitigating MEV-driven centralization pressures.
Proposer Revenue and Key Market Events
Over the past year, validators have earned over 300,000 ETH in total proposer rewards—including both gas priority fees and MEV. While gas fees typically dominate income, periods of market volatility saw MEV payouts far exceed them.
Three major events stand out:
- November 9, 2022: In the aftermath of the FTX collapse, five days of cascading liquidations led to 14,585 ETH in total payments to proposers.
- March 11, 2023: The SVB bank run and USDC depeg triggered a surge in on-chain activity, resulting in 7,694 ETH distributed to proposers.
- July 30, 2023: Following a Vyper compiler bug exploited across DeFi protocols, arbitrageurs raced to rebalance Curve pools. This event generated 7,187 ETH in proposer revenue. One single transaction paid 570 ETH to secure inclusion—marking the second-highest MEV payment in Ethereum history.
Notably, the highest recorded MEV payment—678 ETH—came from white-hat hacker c0ff33b4b3.3th, who discovered and responsibly disclosed a vulnerability. The builder Beaverbuild included this transaction and passed the full reward to the proposer to win the bid.
The Relay Landscape: Growth, Diversification, and Challenges
Relays act as trusted intermediaries between block builders and proposers, validating bids and protecting block contents. At the time of the Merge, seven relays were operational, receiving bids from 27 unique builders.
Flashbots open-sourced its relay implementation a month prior under the LGPL license to encourage competition and diversity. Blocknative followed suit, contributing to an open ecosystem.
Addressing Censorship Concerns
Shortly before the Merge, OFAC added Tornado Cash addresses to its sanctions list. Many relays—including Flashbots—began filtering transactions involving these addresses. Because MEV-Boost requires validators to sign blocks blindly, they lost the ability to include censored transactions.
This sparked debate over censorship resistance. Flashbots Relay remained the only permissionless option at launch. Relayooor emerged on October 26 as the first truly censorship-resistant relay.
Despite this, Flashbots dominated early adoption—peaking at 69% of all blocks relayed on November 11. By November 21, censored relays collectively handled 79% of new blocks.
In response, Flashbots published The Cost of Resilience, advocating for validators to use local block building when MEV-Boost bids fall below a threshold. This preserves network resilience without sacrificing revenue.
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New permissionless relays like Agnostic Relay, ultra sound relay, and Aestus launched in late 2022 and early 2023. Flashbots supported their growth by routing builder traffic their way and publishing operational guides.
Market Diversification and Stability
While Flashbots remains popular, relay diversity has improved significantly. By April 2023, Agnostic and ultra sound relays matched Flashbots in slot share. Today, no single relay exceeds 25% market share, with the top six collectively holding around 90%.
Censored blocks dropped to 17% in April, rebounding slightly to near 30% today. However, fewer than 2% of all blocks contain transactions with sanctioned addresses—indicating minimal real-world impact on transaction inclusion.
Optimistic Relaying: Reducing Latency
To improve speed, ultra sound relay introduced optimistic relaying: forwarding blocks to proposers before full validation. This saves ~100ms—a critical edge in tight markets. Builders must stake collateral to prevent abuse.
Beaverbuild and Titan Builder saw their win rates nearly triple under optimistic relaying. As of now, ultra sound relay remains the only one using this feature at scale.
The April 2 Relay Exploit
On April 2, attackers exploited a flaw in mev-boost-relay to manipulate ultra sound relay and steal ~$20 million from sandwich bots. Malicious proposers submitted invalid headers to win ambiguous blocks, then extracted value by reordering sandwich transactions.
The bug was patched the same day, but network forks increased temporarily. The incident highlighted risks in client diversity and spurred discussions among relay operators about resilience and redundancy.
Evolution of Block Builders
Initially, Flashbots Builder won 95% of MEV-Boost blocks. But builder diversity emerged faster than relay diversity. Within a week, BloXroute captured ~25%, pushing Flashbots below 60%.
Open-sourcing the builder in November accelerated decentralization. Beaverbuild entered in January, leveraging vertical integration as both searcher and builder—giving it exclusive access to high-MEV opportunities.
During volatile events, Beaverbuild temporarily produced 40–50% of blocks, briefly centralizing the market. However, new entrants like rsync (March) and Titan Builder (May) have since diversified the landscape.
Today, the top four builders capture about 90% of market share, driven by intense economic competition.
Key Builder Strategies
- Vertical Integration: Searcher-builders like Beaverbuild gain advantages through exclusive data streams and faster execution—especially valuable in CEX-DEX arbitrage.
- Trust Dynamics: Some searchers distrust searcher-builders due to potential data leaks or competition bias.
- Strategic Bidding: Builder
0x69pioneered subsidized bids—paying more than block value to win slots and attract private order flow. - Order Flow Sharing: To reduce inclusion latency, builders increasingly share order flow—though this complicates tracking.
- Private Order Flow Acquisition: Access to exclusive transaction streams (via RPCs or direct deals) is now essential for competitive block construction.
Data shows that while private transactions make up only 25–35% of total volume, they account for ~80% of total value in blocks.
Searcher Profitability Post-Merge
Atomic MEV: Most Profits Go to Proposers
Using mev-inspect-py, we find atomic MEV (arbitrage, liquidations) generates ~$2M monthly—spiking to $4–6M during volatility.
Proposers captured an estimated $1–4M from atomic MEV—roughly 5–10% of total proposer income (a conservative estimate).
Post-Merge, searchers now pay MEV tips on top of gas fees via bundles. The share going to proposers has shifted dramatically:
- Pre-Merge: <50%
- Early Post-Merge: Dip due to low builder competition
- 2023 Onward: >50%, sometimes reaching 80–95%
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Non-Atomic MEV: Higher Searcher Margins
Cross-market strategies (e.g., CeFi-DeFi arbitrage) are harder to track but more profitable. In Q1 2023:
- CeFi-DeFi arbitrage: $37.8M revenue
- Atomic strategies: $25M revenue
While atomic strategies paid 91–99% of profits to validators, CeFi-DeFi flows paid only 37–77%—indicating higher retained margins for searchers.
Thus, non-atomic MEV likely contributes similarly to proposer income but offers better profitability for searchers.
Looking Ahead: Transparency, Resilience, and Innovation
The Future of PBS
MEV-Boost was designed as a temporary solution until in-protocol PBS matures. However, relays may persist even then—as critical components ensuring decentralization and censorship resistance.
To support ongoing development, the community formed the PBS Guild, a non-commercial R&D fund aiming to raise $1M for independent relays, research, data transparency, and education.
Data Transparency Efforts
Tracking order flow across the MEV stack remains challenging. Flashbots continues advancing transparency through tools like Mempool Dumpster—providing free historical mempool data from multiple node providers.
Final Thoughts
The Merge reshaped Ethereum’s transaction supply chain. While progress is significant, MEV-induced centralization remains a core challenge. The path forward demands continuous research, open dialogue, and community-driven innovation—to preserve Ethereum’s neutrality and decentralization.
Frequently Asked Questions
Q: What is MEV-Boost?
A: MEV-Boost is a software tool enabling Ethereum validators to outsource block construction to specialized builders via auctions, democratizing access to MEV rewards.
Q: How does proposer-builder separation improve decentralization?
A: PBS prevents validators from needing advanced infrastructure to capture MEV, allowing solo stakers to compete fairly and reducing centralization risks.
Q: Why are relays important in the MEV ecosystem?
A: Relays act as neutral intermediaries that verify bids and protect block contents, ensuring trustless communication between builders and proposers.
Q: Can validators censor transactions using MEV-Boost?
A: No—validators sign blocks blindly under MEV-Boost. Censorship occurs only if relays or builders filter transactions.
Q: What is optimistic relaying?
A: It’s a technique where relays forward blocks before full validation to reduce latency. Builders must stake collateral to prevent malicious behavior.
Q: How has searcher revenue changed since the Merge?
A: Atomic MEV profits now mostly go to proposers (50–95%), while non-atomic strategies like CeFi-DeFi arbitrage allow searchers to retain higher margins (23–63%).