The list of currently open tabs is stored temporarily in the web tier, associated with the browser session, and more permanently on the database so that it can be restored after a user logs out of the application.
The data is persisted from the web tier to the database intermittently. As a result, there are cases where the last few changes to the open tabs may not be restored when the user logs in. This is most likely to happen where the session times out or the browser is restarted.
The behavior of tab restoration is different depending on whether it was the result of a browser refresh (F5) or the start of a new session (i.e. the user has logged in).
If the browser is refreshed, tabs are restored to their current state from the web tier session data. No tab changes will be lost.
When a new session starts, usually requiring the user to login, the tabs are restored to their current state using the session data stored on the database.