title: How reliable are Push Notification Systems for Real time Data availability for mobile apps?
body: <p>I am creating a social android+ios app and I am using both apple push notification system and google cloud messaging. I am using push notification both while the app is running and not running. I am not using any web-socket while the app is running so notifications are pushed through apns and gcm all the time.  I know both are not 100 percent reliable and that is where my confusion arises. What does facebook, instagram, snapchat and other apps do to make sure the notifications are always sent. Do they use websockets when the app is running and apns/gcm when its not running? How can I make sure that something like "friend request"  is always notified? Or shall I hit the server now and then to keep the app updated incase it has missed any information which was supposed to be pushed like "friend request"?</p>