Infrastructure

DNS TTL Controls How Long Resolvers Reuse Records

DNS answers are often reused instead of being requested from authoritative servers for every connection. A resolver can keep a record in its cache for a limited period, then answer later queries from that cached copy. The record’s time to live, commonly written as TTL, sets that cache lifetime in seconds. A value of 300 permits caching for up to five minutes, while 3600 permits up to one hour. Once the remaining lifetime reaches zero, the cached record is no longer considered fresh and the resolver normally needs a new answer before serving it again.