Caching web API proxy?

I was wondering if anyone knows of a caching proxy specifically for dealing with API responses?

Ideally, I'd be able to declare what caching policy to use for different API semantics, e.g. cache album art for 1 day, cache favorite tweets for 5 minutes, cache map tiles forever, except invalidate when this other API is called.

I know about using Apache, Squid, etc for caching in general -- I'm just 开发者_开发技巧hoping for something with nicer usage semantics by restricting the design goal to dealing with APIs rather than the web in general.