The server checks the token against the current resource.
If the token hasn't changed, the server returns a "304 Not Modified" response, which tells the browser that the response it has in cache hasn't changed and can be renewed for another 120 seconds.
Check the platform documentation and confirm your settings.
Assume that 120 seconds have passed since the initial fetch and the browser has initiated a new request for the same resource.
First, the browser checks the local cache and finds the previous response.
However, that’s inefficient because if the resource hasn't changed, then there's no reason to download the same information that's already in cache!
That’s the problem that validation tokens, as specified in the ETag header, are designed to solve.