Fee Estimation Bitcoin tx fees are auctioned per-block. Wallets need to estimate the fee rate (sat/vB) needed to confirm within blocks. Bitcoin Core's Returns (BTC/kvB → 10 sat/vB). Algorithm (simplified) 1. Track every tx that enters mempool with its first-seen fee rate. 2. Track which fee rates resulted in confirmation within blocks. 3. For target : find lowest fee rate that successfully confirmed ≥ X% of historical txs within blocks. Modes: (less aggressive), (more buffer). Limitations: - Cold-start: needs 3 hours of running for reliable estimates. - Doesn't see network-wide mempool, only…