When a resource is deemed stale by Cloudflare, and a call happens, Cloudflare fetches content to from the origin, and serves it to the caller. The response is tagged with the EXPIRED header. If someone else makes a call when Cloudflare is fetching the content from origin, Cloudflare serves the old, and stale ressource from its cache, and tags this with “UPDATING”. This is perfectly fine, and the way i want it to work. You only get on call, the first, that hangs a bit, but every other that calls get a stale response and thus not hitting my origin.
What happens under high load? Can it potentially be many that hit my origin? Imagine that 100 hits the resource right after it has become stale at the exact same time (with som miliseconds apart). Does all 100, or a subset of this, calls my origin, or can Cloudflare figure out to only let one of the call through?