What is TTL (Time To Live) in DNS?

TTL (Time To Live) tells recursive DNS servers how long to cache a record before checking for updates.

A TTL of 3600 means cache for one hour. After that, the resolver queries authoritative servers again.

Lower TTL benefits: Faster propagation of changes, more flexibility for updates.

Lower TTL costs: More DNS queries, higher load on authoritative servers, potentially slower lookups.

Higher TTL benefits: Fewer queries, faster responses from cache.

Higher TTL costs: Slower propagation when changes occur.

For email records that rarely change, TTL of 3600 to 86400 seconds is common. Lower temporarily when planning changes.

Short memory means fresh information. Long memory means faster recall but outdated knowledge.