How to properly disable CloudFront caching for API requests

Question

I have AWS CloudFront set up to serve static content and an API server from the same domain. This means I have two behaviors, one serving the API gateway from /api and one serving content from S3 for all other paths.

The problem is that I don't want CF to cache anything from the API server. I was surprised to find that there does not seem to be a "master setting" to completely disable caching behavior; instead the docs refer to using Cache-control: no-cache on the origin or turning on "Cache based on all headers" in the CF behavior.

However, none of these solutions completely satisfy my requirement on simply not caching and passing through all headers. If I add Cache-control: no-cache to my origin, CF seems to respect that, but there is still the question of CF settings. CF has a setting "Cache based on headers: All/None/Whitelist". The docs says that to disable caching, "All" should be used, which makes sense (although a bit vague as compared to having an actual setting: Disable caching: on/off). However, as soon as I set this setting to "All", the entire behavior is disabled and my API requests will not reach the API gateway at all, but default to the S3 behavior used for non-API requests. I cannot find any explanation for this, it's like the entire behavior fails or is disabled without explanation.

The other problem is that headers not present in the "Cache based on" will not only be excluded from caching (which I don't want anyway), but also stripped out of the request before it's forwarded. This may make sense for a cache to work as intended, but since I don't want any caching it's quite frustrating to have to make sure to white-list all the headers I ever use. It would feel much better to rely on "All" than having to make sure the white-list is always up to date.

So:

1) is there a better, clearer way to disable caching completely for one path of a CloudFront distribution? Ideally it shouldn't even rely on the origin setting certain headers, it should just completely disable any attempt to cache requests within the configured path.

2) Why is my entire API gateway target disabled when I select "All" in the "Cache based on headers" box? What's happening here?

Answer 1

Just had the same issue and ended up contacting AWS help on it.

Based on the AWS associate, the reason why "Cache based on headers = All" doesn't work on API gateway is that, forwarding of "Host" header makes it non-applicable.

The way that it worked for us is by setting the TTL on the API gateway behavior to zero, for both Max and min value.