I'm actually having a strange problem with one of my drupal installations. While I was trying to setup nginx for one of my sites, I ran into an issue that only the frontpage wont get cached.
After a bit of debugging, I found out that for some reason drupal always adds an session cookie to the HTTP response header (see screenshot)
This cookie is only added to the frontpage of my site, all other pages do not have it. By adding this cookie, drupal prevents nginx to cache this site, cause I dont want users to be redirected to cached pages if they are logged in.
Someone have an idea where that cookie comes from? I checked other drupal installations, but those don't have this cookie.