Backend & systems·Caching and invalidation
you let the cached value expire after a fixed number of seconds instead of trying to work out exactly when it stopped being true.
Time to live
Also calledTTL, expiry
An expiry stamped on a cache entry, after which it is treated as absent. TTL trades correctness for simplicity: you accept being wrong for up to the TTL in exchange for never having to reason about invalidation. Uniform TTLs on a batch of keys written together will expire together, which is one of the common ways to build yourself a stampede.