I am writing back end for mobile app, we are sending pushes (something like one user add another to buddies) he should accept it or decline via push notification(it is required), server got some feedback from notification, and do something.
I am familiar with two techniques about pushes, first I push directly on device using token, second is abstraction when user subscribes for channel and I send push notification on this channel. Id in my application is email, and I suggest to update device token in the database each time user login, and send push on it, but how should I identify device OS ?(IOS/Android)
1) How to scale it, if user have multiple devices, and when user will logout, and login from other device ?
May be there is common solutions for this problem.