I noticed that if user is logged in and then logged out, it is still listed as "Online" and only removed after some time (15 min?).

I want to remove user from the online list instantly if user clicked "logout"

What is the best way to implement it?
By the way, should I check some aspnet_membership table or dnn_UsersOnline?
It seems that module still uses dnn_UsersOnline, even if according to DotNetNuke Membership.doc  "the DotNetNuke Anonymous Users and UsersOnline tables would no longer be required".

I just started to look at Users Online module and has not been able to find an article that gives a thorough explanation of the mechanism it uses.

My understanding is users do not get deleted from UsersOnline table for the period specified in Host Settings -> Advanced Settings -> Other Settings ->  Users Online Time (Minutes). Instead each time a user performs any type of activity on the site that activity first gets recorded in cach and then a scheduled process called "DotNetNuke.Entities.Users.PurgeUsersOnline" (set to run every minute by defauld in Host Settings - > Scheduling ) extracts that info from UserList Hashtable in servers memory and updates records in UsersOnline table.

I find behavior of UsersOnline to be quite inconsistent. In my testing I saw instances when lastactivitydate does not ger updated on user's logout. Also unless I am missing something it sounds like a user would be listed in 'online' status even after that user loggs out (for the period specified in Users Online Time settings).

If anyone came across technical notes on usersonline, please share.