Logged In User Cache

What Does Logged In User Cache Do? 

When you activate this option, it creates a set of cache files for each user. This is great when you have user-specific content on your site. The site will also be cached as normal,  for any user that is not logged in, using one set of cache files.

As of WP Rocket 2.9 you can choose to use the same set of cached files for every logged in user, instead of a set of cache files per user:

Logged in user cache is useful when you have a membership site or similar - when users must log in to see content.

There are a couple of considerations specific to using this option:

User is not correctly logged out

If there seems to be confusion about the logged in or logged out status of a user, it could be due to the fact that you have custom login or logout pages.  

WP Rocket does not cache the default WordPress login/logout URLs. But if you are using custom URLs, WP Rocket won't be aware of them, so you should manually exclude those URLs from the cache:
http://docs.wp-rocket.me/article/54-exclude-pages-from-the-cache

Custom cookies

If you are using a plugin that sets some custom cookies for detecting logged in / logged out status, you may need to add those to the Advanced option:
Don't cache pages that use the following cookies

Login / Logout Menu Links

If you are looking for a plugin that can dynamically add login / logout links to your menu, we recommend the following because it is cache-friendly:
https://wordpress.org/plugins/baw-login-logout-menu/

Preloading

Note that the preload bot CANNOT "log in" as a user to preload individual users' caches. It will just preload the general cache as usual.