Bitcoin Core has recently implemented a significant update called the “Cluster Mempool,” which reevaluates and reforms the method of organizing and prioritizing pending transactions in the mempool. Developed by Suhas Daftuar and Peter Wuille, this system aims to simplify the overall mempool structure, better align transaction ordering with miners’ interests, and enhance the security of second-layer protocols. The update was integrated into Bitcoin Core in November 2025.
The mempool temporarily stores all unconfirmed transactions, allowing miners and nodes to estimate fees, verify transactions, and select appropriate transactions for block creation. Previously, Bitcoin’s mempool used two separate criteria for ordering transactions: ancestor fee rate and descendant fee rate. These conflicting standards often caused difficulties for miners and users alike.
The new Cluster Mempool concept centers around “clusters,” which are groups of interconnected pending transactions. Each cluster is divided into smaller segments called “chunks,” arranged according to fee priority. This approach improves the efficiency of mempool ordering, better serves miners’ interests, enhances block creation performance, and reduces uncertainty.
Additionally, the system simplifies transaction space and ordering decisions while increasing transparency in transaction replacement and eviction processes—crucial for the security of second-layer protocols. This new mempool structure helps reduce mining centralization, offers users more reliable fee estimates, and strengthens Bitcoin’s overall integrity.
This advancement marks a vital milestone for Bitcoin’s future, making the network more stable, fair, and secure amid growing popularity and transaction volumes. Thanks to the Cluster Mempool, transaction processing on the Bitcoin network will become more efficient and predictable.
Source: bitcoinmagazine
