[lucaspardue]

This depends on how the proxy is configured to behave. One common pattern is to have a protocol terminating proxy talk to the client. Other component(s) sit behind this and they could be other parts of the system, tiers of caches or tiers of CDNs.

Even if the proxy does cache locally to memory or disk. Without infinite space, there will be some chance of cache eviction and a need to fetch from the upstream again.

Our scenarios are different ends of a broad spectrum, and there's a lot in between. Which is why getting prioritisation right is a hard nut to crack.