The CachingHttpClient internally uses HttpCache. That class, however, has been designed as a public (shared; surrogate) cache.

In this "downstream" caching use case, however, it would be valuable if we

• could make the cache store private responses, possibly even by default,
• enforce a "greedy" caching strategy, i. e. a minimum TTL to apply regardless of what the upstream server sent
• support stale-while-revalidate behavior 🆒

Client-side caching in the HttpClient is useful in µService architectures where you possibly hit a lot of backend APIs; stale-while-revalidate and stale-if-error may further improve performance or even save the day when a backend service goes down.