What Is a “Mempool” and How Does RBF Interact with It?

The mempool is a node's temporary holding area for unconfirmed, valid transactions awaiting inclusion in a block. RBF is a mempool policy that governs how nodes handle conflicting transactions.

When an RBF replacement transaction is broadcast, a node supporting RBF will remove the original, lower-fee transaction from its mempool and replace it with the new, higher-fee version. This process ensures miners prioritize the most economically attractive transaction.