Hello guys,

I'm not able to find any information about how the proxy_cache_background_update works. Official documentation says:

Allows starting a background subrequest to update an expired cache item, while a stale cached response is returned to the client. Note that it is necessary to allow the usage of a stale cached response when it is being updated.

Ok I get this, but how does it work in detail? Is the background process checking all proxy cache keys in RAM? Can someone explain this in more detail please? I've activated this option but still receiving EXPIRED responses on the content I've checked.

Cheers,
Szop