There are quite a few caching options out there, and we frequently combine several services to cache every little piece of a site. Think about it: standard Drupal cache, Varnish, Memcache, Redis, various files coming from CDNs, and more.
All week, members of the CivicActions team will be in Austin, Texas for DrupalCon 2014. If you plan on attending, you can find us at booth 608 in the Exhibit Hall.