Time To Live (TTL)¶
Time To Live, abbreviated TTL, is a value that defines how long a piece of data remains valid before it expires and must be refreshed or discarded. It is expressed in seconds in most contexts.
TTL appears across many layers of a PHP application: cache entries (Redis, Memcached, APCu), DNS records, HTTP cache headers such as Cache-Control: max-age, JSON Web Tokens, session lifetimes, and idempotency key storage.
A short TTL reduces stale data at the cost of more frequent recomputation or re-fetching. A long TTL improves performance but risks serving outdated information.
Related : Cache, Idempotent, Session, JSON Web Token (JWT), HTTP Headers, Domain Name System (DNS), Memoization
