Mempool (Memory Pool)
Transaction waiting room before inclusion in a block — visible to all, MEV hunting ground.
Mempool (Memory Pool) is a temporary "waiting room" where transactions wait until included in a block by miners or validators.
How it works: 1. You send a transaction → broadcast to network 2. Transaction enters mempool of every node 3. Miners/validators choose transactions for inclusion (usually by gas price) 4. Transaction enters block → confirmed 5. Transaction stays in mempool if gas price too low → "stuck"
Why mempool is transparent:
•All mempool transactions are visible to everyone
•MEV bots constantly scan mempool looking for opportunities
•Front-running is possible because you see transaction before it's confirmed
Mempool size:
•Large mempool = high demand for blockspace = high gas price
•Small mempool = low demand = cheap gas
Protection from MEV:
•Flashbots Protect RPC — sends transaction directly to validator, not public mempool
•Slippage protection on DEXs
•Private RPC providers
Bitcoin mempool: typically 50,000–200,000 transactions during high activity periods.