Mempool

Mempool is a collection of unconfirmed transactions that a particular node has accepted after validation but that have not yet been included in a confirmed block.

A mempool is not necessarily one global queue shared identically by the entire network. Each node can maintain its own transaction set and apply its own implementation-specific policies for admission, prioritization, and expiration.

Role of the mempool

When a user broadcasts a transaction, it can propagate between nodes and enter their mempools. A block producer then selects eligible transactions from the available set.

During periods of high demand, mempools can grow substantially. This can increase competition for limited block space and result in higher transaction fees.