Mempool refers to a mechanism used by a cryptocurrency’s node to store validated but unconfirmed transactions. Coined from the combination of memory and pool, Mempool acts as a staging area for valid transactions yet to be added to a valid block.

How does a Mempool work?

A blockchain network operates such that individual transactions are broadcast to a single node, passing it up to other nodes throughout the entire network. The cryptocurrency’s node serves as a buffer zone for transactions, ensuring that they are not double-spent and that the signatures provided are accurate. Given the growing number of transaction confirmations usually executed at a specified time interval, these nodes tend to receive a lot of transactions waiting to be confirmed. The amount of memory available dedicated to storing transactions on the node determines the number of unconfirmed transactions held in the mempool, i.e. the mempool size.

Mempool configuration differs since miners set mempool conditions in various ways. In many nodes, transactions with higher fees are first considered, alongside factors such as block size, block space and network throughput, which means more rewards for miners. Many crypto traders try to figure out the right amount of transaction fee using a mempool explorer as transactions are discarded when the mempool reaches high thresholds, consuming vast amounts of memory.

What Should I Do If My Transaction is stuck in the Mempool?

Yes, transactions can be stuck in a mempool. Solutions such as Opt-In Replace-by-Free (RBF), Child Pays for Parent (CPFP), and Transaction Accelerator Services have been developed to tackle such situations.