I don’t understand what is meant in Rails Guide about caching:
Unfortunately, it can’t be applied to every situation
(such as pages that need authentication) and since the webserver is literally
just serving a file from the filesystem, cache expiration is an issue
that needs to be dealt with.
What are “pages that require authentication”? Are they just the pages
with a form for authentication? Like the main page of facebook.com when
you are not logged in? Then why is it impossible to cache it? It is the
best page for caching because it is always the same, it has only the
html-form. Unlike the profile page that has a lot of fields that are
changed very frequently.