Bitcoin Magazine Podcast

Cluster Mempool Explained & How Bitcoin Fees Actually Work w/Bitcoin Core Dev Peter Wuille

Feb 10, 2026
Peter Wuille, researcher at Chaincode Labs and long-time Bitcoin Core developer behind SegWit, explains cluster mempool: grouping related transactions into 64-transaction clusters. He outlines why precomputed total ordering fixes eviction and mining inconsistencies. Short sentences explore optimal per-cluster ordering, fee strategies like CPFP, and how this future-proofs Bitcoin for Layer 2 and miner-aligned incentives.
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INSIGHT

Single Total Ordering Fixes Mempool Inconsistency

  • Bitcoin Core used different orderings for mining vs eviction, causing inconsistent and sometimes perverse outcomes.
  • Precomputing a single total ordering would make mining, eviction, and propagation decisions consistent and predictable.
INSIGHT

Unified Ordering Solves Multiple Mempool Problems

  • Many subsystems use ad-hoc heuristics to compare transaction quality, causing inconsistent behavior.
  • A unified ordering exposes effective fee rates (including CPFP) and simplifies propagation, fee estimation, and wallet logic.
ANECDOTE

Pathological Eviction Example Sparked Reform

  • Suoz discovered pathological cases where eviction removed the very transaction a miner would choose first.
  • That observation catalyzed the effort to redesign mempool ordering.
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