Upstream: $upstream_cache_age variable. The variable reflects response age, including the time spent in the cache and the upstream response age as obtained from the "Age" header. If the response wasn't cached, the variable reflects the "Age" header of the upstream response. If the intended use case is to cache responses as per HTTP/1.1 caching model, the $upstream_cache_age variable can be used to provide the "Age" header with the "add_header" directive, such as: add_header Age $upstream_cache_age; This now removes the "Age" header if it was present. Further, the "expires" directives now removes the "Age" header if it was present in the response, as the "expires" directive assumes zero age when it adds "Expires" and "Cache-Control" headers.