How can I know that a Firebase Cloud Messaging token is out of use?

A single user can have multiple devices connected to his account. Because of that he can have multiple cloud messaging tokens. Everytime the user opens the app the token from that device is send to the app server and saved there.

What happens if a user uninstalls the app from one of his devices? I have no chance to tell the server that the token is not longer in use. Can it occure that I notify an other user instead since this other user has acquired the not longer used token from the original user?

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