Glossary
Mempool
The in-memory queue of unconfirmed transactions that a node has seen but that have not yet been included in a block.
When you send a transaction, it doesn't go straight into a block — it lands in the mempool, the buffer of pending transactions each node maintains. Block producers pull from their mempool when constructing the next block, generally prioritizing higher-fee transactions.
The mempool is also where MEV happens: it is publicly observable on most chains, so searchers can see profitable transactions before they confirm and try to front-run, back-run, or sandwich them.