The Searcher Stack

Mempool subscribers, simulation engines, bundle submission paths, and the builder relationships that make profitable MEV possible.

35 min · expert · part of MEV Searcher Strategies

What a Searcher Actually Does

MEV — Maximal Extractable Value — is the profit a sophisticated actor can capture by reordering, inserting, or censoring transactions inside a block. The actor doing the capturing is called a **searcher**. They are not validators, not block builders, not relays. They are independent firms (or solo coders) who run software that watches the network for opportunities, simulates them locally, and submits bundles to whoever will include them. By mid-2025 cumulative Ethereum MEV extracted since Flashbots started measuring crossed $1.8 billion, according to Eigenphi, Flashbots' public dashboards, and EthMEV. Solana's MEV economy is younger but exploded after Jito launched its priority-fee auction; sandwich bots alone earned an estimated $370-500 million on Solana between January 2024 and May 2025 (Eigenphi data, cross-checked against Jito's own bundle stats). A working searcher operation has four pillars: (1) **observation** — a node that sees pending transactions and new blocks before the average user does; (2) **simulation** — a local EVM that can execute a candidate transaction sequence against the current state to compute exact profit; (3) **strategy** — the algorithm that decides which opportunity is worth pursuing; and (4) **submission** — the path that gets the bundle into a block. Each pillar is a research problem. This lesson walks each layer of the stack: what software is used, what the tradeoffs are, and what the operational reality looks like for someone running a searcher in 2025-2026. It is meant for readers who want to understand the engineering, not glamorize the work — Lesson 5 returns to the ethics in detail.

Also in this lesson

Layer 1: Mempool Subscribers and Node Choice
Layer 2: Simulation Engines
Layer 3: Bundle Submission and Builder Relationships
The Numbers: What a Searcher Actually Earns
For Deeper Reading

Key terms

MEV (Maximal Extractable Value): The profit a sophisticated actor can capture by reordering, inserting, or censoring transactions inside a block. Cumulative measurable Ethereum MEV exceeded $1.8B by mid-2025.
Searcher: An independent firm or individual who monitors the mempool, simulates opportunities locally, and submits bundles to builders for inclusion in blocks. The "labor" side of MEV extraction.
Mempool: The pool of pending transactions broadcast to the network but not yet included in a block. Public mempool transactions are visible to anyone; private flow bypasses it.
revm: A Rust implementation of the EVM maintained by Paradigm. The de facto simulation engine for modern searcher stacks because it is 10-50x faster than geth interpretation for repeated simulation.
Bundle: A list of transactions submitted atomically to a builder. Either all execute in the specified order at the top of a target block, or the whole bundle is excluded. Atomicity is what makes MEV economically viable.
Builder: A specialized firm that assembles Ethereum blocks from mempool transactions and searcher bundles, then sells the assembled block to validators via MEV-Boost. Major builders: Beaverbuild, Titan, Flashbots, rsync.
Flashbots Builder API: The original searcher submission endpoint, exposing eth_sendBundle and mev_sendBundle methods. Flashbots historically held 40-60% MEV-Boost share; competition has reduced that to roughly 15-25% by 2025-2026.
Coinbase transfer / priority fee: The payment a searcher makes to the block proposer (validator) in exchange for including the bundle. Typically 60-90% of gross extracted value.
Latency budget: The 100-400ms window between observing a transaction in the mempool and submitting a competing bundle. Every component of the searcher stack consumes part of this budget.
MEV-Share: Flashbots' opt-in protocol (2023) that matches user transactions with searcher bundles and refunds a share of captured MEV to the original user. Constructive MEV alternative to extractive private-mempool routing.

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Educational only — not financial advice.