For example,
A has a playfab account for our game and his account has a facebook account linked as well. One day, he tries to run the game on both of his IOS devices and login his account by using the same linked facebook account. What will happen? Can both of the devices successfully login to the game and update his player variables at the same time?
The current design of the session system allows for multiple device usage. This was specifically done to support games which have that as a requirement. So right now, yes, the player would be logged into his account on both devices. We'll be updating soon with a new session system which allows titles to choose to invalidate old sessions on a new sign-in. In the meantime, a simple check for this would be to record the sign-in time from the Login call locally, and to check it at key points in the play experience (every few minutes), via the account info query, to see if it's the same.
