We are using Xtify services for Push notification in our company. And we keep the XID associated with a customer_id.
We dont have a way to find out if the customer has uninstalled the app. Although it seems like Xtify has a way of knowing this reactively when the push notification fails Ref: Xtify : When will a Xid be marked as Inactive
So basically Im after a way that can associate something of an XtifyID with a specific app user and be notified by Xtify when that customer logs out of that app on that device so we prune our XID list.