On: A Complete Guide to Rails Caching

This is because caching should be done as coarsely as possible. Caching views and entire pages is the common case.

Exactly - why did page caching get removed from rails core?

So what’s the best approach for caching API responses?

An api response isn't any different from a web page insofar as infrastructure is concerned. HTTP caching is usually my first choice when I have the wherewithal to do that.

[Edit: conditional responses are probably the best way to go – save the bandwidth.]