A system and method determines when the entries of a reply cache, organized into microcaches each of which is allocated to a client connection, may be retired or released, thereby freeing up memory structures. A plurality of connection statistics are defined and tracked for each microcache and for the entries of the microcache. The connection statistics indicate the value of the microcache and its entries to the client. The connection statistics include a measure of the time since the last idempotent or non-idempotent request (TOLR) was received, and a count of the number of idempotent requests that have been received since the last non-idempotent request (RISLR). A microcache with a TOLR time and a RISLR count that exceed respective thresholds may be expired and removed from the reply cache.