Bitcoin Core just merged cluster mempool. The largest internal refactor in years. Most people have no idea it happened. Here's why it's one of the most important things Bitcoin Core has built.

The mempool is Bitcoin's waiting room. Every unconfirmed transaction sits here until a miner includes it in a block. How the mempool orders and evicts transactions directly affects fee estimation, RBF, and block construction.

The old mempool tracked transactions individually and by ancestor/descendant relationships. This worked, but made it hard to reason about optimal block construction and fee-rate-based eviction. Cluster mempool groups related transactions together and sorts them into the optimal order for mining.

What this means is: - Better block templates (miners make more in fees) - More accurate fee estimation (users pay less) - Cleaner RBF/CPFP handling (transactions replace more predictably) For protocols settling natively on Bitcoin L1, this matters a lot. At Ducat, every UNIT loan flows through the mempool. Better fee estimation and more predictable RBF means cheaper, more reliable fee estimates when taking on a loan.

Cluster mempool is staged for Bitcoin Core 31.0. Work continues on replacing the initial candidate-set search with a spanning-forest linearization algorithm for even better performance.

This is the important infrastructure work that determines how efficiently every single Bitcoin transaction gets processed.