Speak the Language of MEV
Algorithmic trading has its own vocabulary. We've compiled the essential terms you need to know to navigate the dark forest of Ethereum and beyond.
MEV (Maximum Extractable Value)
Core ConceptsThe maximum value that can be extracted from block production in excess of the standard block reward and gas fees by including, excluding, and changing the order of transactions in a block.
Front-Running
StrategiesA trading strategy where a bot detects a large pending transaction and places its own transaction with a higher gas fee to get executed first, usually to buy a token before the price goes up.
Sandwich Attack
StrategiesA combination of front-running and back-running. The attacker buys before a victim's trade and sells immediately after, pocketing the price difference caused by the victim's slippage.
Flashbots
InfrastructureA research and development organization formed to mitigate the negative externalities of current MEV extraction techniques and avoid the existential risks MEV could cause to state-rich blockchains like Ethereum.
Private Relay
InfrastructureA communication channel that allows searchers to send transaction bundles directly to block builders/validators, bypassing the public mempool to avoid being front-run or having strategies simulated.
Bundle
Core ConceptsA collection of transactions grouped together and submitted to a block builder. Bundles are atomic, meaning either all transactions in the bundle are included in the block in the specific order, or none are.
Base Fee
Gas & FeesThe minimum gas price required to include a transaction in a block, determined by the protocol (EIP-1559). It is burned and not paid to validators.
Priority Fee (Miner Tip)
Gas & FeesAn additional fee paid directly to the validator to incentivize them to prioritize your transaction over others.
Searcher
RolesAn automated bot or entity that monitors the mempool for MEV opportunities and submits bundles to builders to capture that value.
Builder
RolesA specialized actor that accepts bundles from searchers and constructs full blocks to maximize profit, which are then proposed by validators.
Mempool
InfrastructureA "waiting room" for pending transactions that have been broadcast to the network but not yet included in a block.
Slippage
TradingThe difference between the expected price of a trade and the price at which the trade is executed. MEV bots often exploit high slippage settings.
JIT Liquidity (Just-In-Time)
StrategiesA strategy where a liquidity provider adds liquidity to a pool immediately before a large trade and removes it immediately after, capturing the trading fees.
Backrunning
StrategiesSubmitting a transaction immediately after a target transaction in the same block to capture price impact or arbitrage opportunities. Generally considered ethical and used by FRB Agent.
Liquidation
StrategiesClosing under-collateralized lending positions on protocols like Aave or Compound to claim the liquidation bonus. A protocol-positive MEV strategy that maintains lending market health.
Flashbots Bundle
InfrastructureA group of transactions submitted atomically to Flashbots block builders. Either all transactions execute in the specified order or none do — eliminating partial-fill risk.
Jito Bundle
InfrastructureSolana's equivalent of Flashbots bundles, submitted via the Jito Block Engine. Enables atomic multi-transaction execution with tip-based prioritization on Solana.
MEV-Boost
InfrastructureOpen-source middleware run by Ethereum validators that lets them outsource block construction to specialized builders, separating block proposing from block building (PBS).
Block Builder
RolesA specialized actor in Ethereum's post-Merge architecture that constructs full blocks from searcher bundles and submits them to validators via MEV-Boost relays.
Validator
RolesA network participant that proposes and attests to blocks. On Ethereum (post-Merge), validators stake 32 ETH and receive priority fees plus MEV-Boost rewards.
Inclusion Rate
TradingThe percentage of submitted bundles that successfully land in a block. FRB Agent achieves ~94% inclusion on Ethereum via Flashbots and ~91% on Solana via Jito.
Revert Protection
InfrastructureA bundle setting that prevents the transaction from being included if it would revert (fail). Saves gas on failed attempts. Available on Flashbots, Beaver, and Titan relays.
Public Mempool
InfrastructureThe shared queue of pending transactions visible to all nodes before block inclusion. Transactions here are vulnerable to sandwich attacks and front-running.
PBS (Proposer-Builder Separation)
Core ConceptsEthereum's post-Merge architecture pattern where block proposing (validator) and block building (builder) are separated, enabling MEV-Boost's competitive marketplace.
Atomic Execution
Core ConceptsA guarantee that a sequence of transactions either all succeed in the specified order or all fail together. Critical for arbitrage bundles where partial execution would create losses.
Tip (Solana)
Gas & FeesA small payment included in a Jito bundle to prioritize inclusion. Tips compete in real-time auctions; FRB Agent automatically optimizes tip size based on bundle expected value.
Gas War / PGA (Priority Gas Auction)
TradingA bidding war on the public mempool where searchers escalate gas fees to outbid each other for the same opportunity. Wasteful — private bundles eliminate this entirely.
Honeypot Token
TradingA scam token contract that prevents holders from selling. FRB Agent's policy engine includes a honeypot blocklist and runs simulation checks before any live trade.
Anvil Fork
InfrastructureFoundry's local Ethereum testnet that forks mainnet state in real-time. FRB Agent uses Anvil for risk-free strategy simulation against current chain conditions.
WSS (WebSocket)
InfrastructureA persistent bidirectional connection used by MEV bots to subscribe to real-time mempool events. Lower latency than HTTP polling; FRB Agent benchmarks WSS endpoints by region.
SUAVE
InfrastructureSingle Unified Auction for Value Expression — Flashbots' decentralized chain for sequencing and MEV redistribution. Aims to standardize MEV markets across rollups.
Bundle Refund
Gas & FeesWhen a builder rebates a portion of MEV revenue back to the searcher whose transaction generated it. FRB Agent surfaces realized refunds in its Ops Pulse telemetry.
Non-Custodial
Core ConceptsA software model where the user retains exclusive control of private keys. FRB Agent is non-custodial — keys never leave the user's machine and the publisher cannot access funds.