This article is a little old although could point you in the direction which responses are cached and potentially how to create your own caching rules for API responses using an Action Filter
Add HTTP Caching to the Episerver Content Delivery API – Matthew Mols (mmols.io)
In reagrds of setting up Page Rules for API responses it suggested this can only be done via a support request
Is there any docs or tuto on how Episerver generates etag header to tell Cloudlfare if cached response is still valid?
We are enriching content in content delivery api response with an additional data, which is changing from request to request.
But at cache check Cloudlare always says "REVALIDATED", which mean (as I understood) that it consider existing cached response as a valid one.
And as a result we always get that first cached value from back end.