The amount of time (in seconds) a response has been cached (in all nodes).
Fastly reads this header from responses. It is defined by an external standard.
For example, if a resource is served with the following response headers:
Cache-Control: max-age=30Age: 10
then Fastly will set
20 (30-10), and record the
Age header as part of the cached object. A request received 8 seconds later for the same resource would see a cache hit with an
When a resource has passed its TTL and is therefore stale, Fastly will attempt to revalidate it if the resource includes a
ETag header. If the response to a revalidation request is
304 Not Modified, we will update the stored object's TTL, and reset the
Age to the value included in the revalidation response, or zero if there is no
Age header on the new response.
In the case of revalidation requests conducted in the background (as a result of
stale-while-revalidate), a successful revalidation will not reset the value of
When the TTL of a resource is determined by an
Expires header, Fastly will initialise the cache object's
Age to zero, regardless of the value of the
Age header on the backend response.