What is the best way to implement a 'last seen' function in a django web app?
A hashmap or a queue in memory with a task running every hour or so to persist it.
I have a running django/apache2 + memcached app (ubuntu) and would like to keep track of logged in users that are online.
What would be the best way to track this? 
I would prefer not writing to the database each time a logged in user loads a page; but what other options are there?