Bitcoin Core getmempoolinfo RPC: Capacity and Fee Guide

This guide explains Bitcoin Core getmempoolinfo RPC in plain English. It shows what the command does, what its result means and what it cannot prove.

Count and virtual bytes

size is transaction count; bytes is the sum of BIP 141 virtual transaction sizes. Neither equals allocator memory. Track both because batching, witness composition and transaction shapes can change byte pressure without proportional count movement.

Usage and maximum

usage measures dynamic mempool memory while maxmempool is the configured ceiling. The relationship is not a simple percentage of transaction bytes because indexes and objects add overhead. Leave host headroom for database cache, peers, wallets and the operating system.

Fee floors

mempoolminfee is the higher of the relay floor and the rolling minimum induced by mempool pressure. Minrelaytxfee is the ordinary local relay floor. Historical units are BTC/kB. Convert carefully and never advertise one node’s value as a network-wide required fee.

Eviction behaviour

When memory pressure forces eviction, the rolling minimum can rise and then decay over time. Transactions missing after pressure may have been evicted rather than rejected by consensus. Record the preceding floor, usage, configuration and transaction package before diagnosing.

Node-local demand

Peers relay different subsets under different policies and timing, so mempools diverge. Compare several controlled nodes and fee-estimation evidence. A low value after restart or network isolation is not evidence that demand disappeared.

Alert design

Warn on sustained usage near capacity, rising floors, unexpected configuration changes and disagreement with peer nodes. Use duration and service impact. Automatically enlarging maxmempool can exhaust hosts and does not solve poor fee or transaction policy.

How specialists test it

Operators test the command on a non-production node first. They check a normal reply, an invalid request, a timeout and a restart. This shows what the response means and prevents one local result from being mistaken for a network-wide outcome.

Conclusion

getmempoolinfo provides a compact capacity and fee-pressure view, but only when each field’s unit and node-local policy meaning remain explicit. It is not a global demand oracle.