Backend & systems·Caching and invalidation
you keep the values in the application's own memory, so lookups are free and every instance ends up with a slightly different copy.
In-process cache
Also calledlocal cache, near cache
A cache living inside the service process. It is the fastest option available, with no network hop, and it is the only one that keeps working when the shared cache is unreachable. The cost is that it multiplies by instance count: N replicas mean N copies to warm, N copies to invalidate, and N chances to serve a different answer to two users at the same moment.