I'm implementing a sort of url-shortener service. What happens is that I have some backend app server that takes in a request, does some computation and returns a 301 redirected url back upstream to an nginx frontend:

request --->   nginx  ---->  app_server

What I want to be able to do is cache this returned 301 url for the same request (a specific url with a "short code").

Does nginx do this caching automatically? Or should I drop in something like varnish in between nginx and the app_server? I can easily cache this in memcache, but that would require hitting the app_server, which I'm sure can be dispensed with after the first request.

Thanks.