NonTTL

NonTTL is a term used to describe data entries or cache items that are not assigned a time-to-live (TTL) expiration. In systems that support TTL, each item typically has an expiry time after which it becomes invalid or is evicted. NonTTL items, by contrast, do not expire automatically and remain in the store until they are explicitly updated, invalidated, or removed by memory pressure or administrative action.

Common contexts for nonTTL items include distributed caches and storage layers, database caches, and some HTTP caching configurations. In Redis, for example, keys may be created without an expiry, which effectively makes them nonTTL; in other systems, nonTTL may be implemented through configuration flags or special policies. NonTTL behavior can also interact with cache invalidation strategies, where certain data is considered stable and refreshed only upon explicit changes rather than on a timer.

Implications of using nonTTL data include reduced overhead from avoiding frequent re-fetches or reloads, but at the risk of serving stale data if the underlying source changes and no invalidation occurs. Memory usage can also become a concern if too many nonTTL entries accumulate. Design considerations often involve separating nonTTL data from volatile, TTL-bound data, implementing robust invalidation or refresh mechanisms, and monitoring memory and staleness.

Best practices typically include using nonTTL for static or rarely changing configuration, feature flags, or long-lived reference data; pairing nonTTL with explicit invalidation on updates; and ensuring clear pathways to purge or refresh nonTTL data when necessary. See also TTL, cache invalidation, and eviction policies.