How Does a Node’s Mempool Size Limit Influence Its RBF Relay Policy?

A node's mempool size limit (typically measured in megabytes) directly influences its RBF relay policy during network congestion. When the mempool is full, the node must evict lower-fee transactions to make room for new, higher-fee ones.

The RBF policy ensures that if a new transaction is a replacement, it must meet the minimum fee-increase rule to justify the eviction of the old transaction, thus optimizing the use of the limited mempool space for the most profitable transactions.