Browser cache times when using Cloudfront

Earlier last year (2020) I had a problem to solve — cache particular content in Cloudfront for as long as possible (and rely on invalidations when needed), but at the same time cache that content only for an hour on the browser.

The problem lies in the way Cloudfront, or almost any other proxy server for that matter, handles the content — the response from the origin is cached together with all headers. Then when we ask for that content, the proxy replies with the same headers, which obviously includes an old Date header. In addition, the proxy also adds an Age header that shows how old the content has been since it was retrieved from the origin.

That of course is the right thing to do, but when you have sayCache-Control: max-age=3600 and Age: 3900, that means your content has already expired and won’t be cached locally by the client (browser):

This simple function above does everything we needed to simply have this kind of header output:

where Fri, 29 Oct 2021 01:21:19 GMT is the current date and time.
The browser will cache this content for exactly 1 hour and we have some happy engineers :)

The end.

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