Environment variables
Starting in version 5.11.0, caches can be controlled via environment variables.
All caches have the default length of 200000 and the the default max age of 1800 seconds. These defaults can be overridden using the environment variables CACHE_MAX_LEN and CACHE_MAX_AGE_SECONDS respectively.
Values for specific caches can be set using:
DNS_CACHE_MAX_LENDNS_CACHE_MAX_AGE_SECONDSDNSSEC_CACHE_MAX_LENDNSSEC_CACHE_MAX_AGE_SECONDSSMTP_CACHE_MAX_LENSMTP_CACHE_MAX_AGE_SECONDS