When would you NOT want to use memcached in a Ruby on Rails app?

Question

Assuming a MySQL datastore, when would you NOT want to use memcached in a Ruby on Rails app?

Answer 1

Don't use memcached if your application is able to handle all requests quickly. Adding memcached is extra mental overhead when it comes to coding your app, so don't do it unless you need it.

Scaling's "one swell problem to have".