[angelblue05]

The api key is generated upon login. You should reuse the same key unless you explicitly have a way to sign out the user or unless the user's password is changed server side (I believe it revokes the token automatically).

If you have a user selection option, you'll need to authenticate the selected user in the event the user has no api key saved client side. You should not use the same api key for all users. Hope this helps.