forExpires
forExpires is a term used in software design to describe a contract that attaches an expiration policy to a resource, such as a cache entry, a session token, or temporary data. The concept separates the content from its lifetime, enabling predictable invalidation and resource reclamation.
Core components typically include:
- expiryTime: a timestamp after which the resource is considered expired.
- ttl (time-to-live): a duration used to compute expiryTime from an origin time.
- policy: determines how expiry behaves, commonly absolute (fixed expiry) or sliding (extends on access).
- lastAccess or lastRenewal: records the most recent access or renewal event.
- renewal hook: an optional function to refresh or revalidate the resource before expiration.
Behavior: isExpired(now) returns true if now is at or past expiryTime. On access, a sliding policy may
Applications: forExpires is used in caching layers, session management, and temporary tokens, where predictable lifetimes help
Implementation notes: use a consistent time source, handle clock skew, store expiry state with the resource,
Variants and related terms: absolute vs sliding expiration; TTL; renewal strategies; refresh tokens.
See also: caching, token expiration, expiration policies, TTL.