Mempool is a storage facility temporarily storing all unconfirmed transactions with digital coins.

The Bitcoin network has a complex architecture, thanks to its stability and security ensured by its functional elements. One of the parts is the mempool.

How is Mempool used?

The operating principle of Mempool is that system participants, when making a payment, expect confirmation of the transaction each time. To do this, perform the following sequence of actions:

• payment is created;
• the transaction is signed by a system participant using a secret key;
• the transaction is broadcast to the Bitcoin network and prepared for verification.

The payment is considered incomplete until the miner confirms its authenticity. At this stage, all transactions are stored in the Mempool storage. Moreover, the filter is not only based on the date of creation. When the storage is overloaded, miners can prioritize the queue based on the commission size. Thus, small and cheap transactions are pushed to the back of the queue. For a transaction to be considered valid, it must be confirmed at least 6 times - this number is considered optimal. However, this number can be individually adjusted from 3 to several hundred confirmations on different services where cryptocurrency payments are accepted. Everything usually depends on the transaction amount.

Transition from the mempool and its problems

Once a transaction is verified, it is moved out of the mempool and becomes one of the block elements. Considering the throughput speed of the Bitcoin network, the problem of mempool congestion still remains relevant. If the mempool is overloaded, the transaction does not disappear, but the user will need to perform a relay.