Is the minimum fee consensus, just policy, or both?

Question

Intuitively, I think minRelayFee is policy while minBlockTxFee is validation, but DEFAULT_MIN_RELAY_TX_FEE is in validation.h while DEFAULT_BLOCK_MIN_TX_FEE is in policy.h.

Answer 1

Both are policy. Both are about the same rule, just concern different parts of the code.

DEFAULT_MIN_RELAY_TX_FEE is about transaction relay (don't relay transactions that pay less than 1000 satoshis per kilo-vbyte), while DEFAULT_BLOCK_MIN_TX_FEE is about block creation (don't include transactions paying less than 1000 satoshis per kilo-vbyte in block templates).