Apple Push Notification reliablity I have one app supported on both Android and iOS. The app needs a background service which hits a remote server every minute. The job is simple for Android app but since background tasking is not supported in iOS I need to employ push notifications for iOS app. Apple says that the delivery of push notification is never acknowledged. I cannot afford push notification failure since I need to send a very crucial message through notification. My questions are:

1) What is the failure rate of push notifications? 

2) Are push notifications always reliable to send important messages?

3) Assume that the server which is supposed to send push notifications sends a large number of push notifications every minute. What are the chances of push notification failure in such a case?

4) Which circumstances cause push notification delivery to fail?

If you have any useful resources please provide the same. Thanks.
The notifications come through 99.9%, I think the 0.01% is when your phone doesn't have network. That is the only reason it won't go through, unless you have a poor server with 10000 requests per second then yes that will fail. 

So for best results just get a good server. I don't think you can help people with cellular coverage. Even if you did run in background they won't be able to pull data from internet if they don't have cellular network. 

Apple just wants you to not rely on it 100%, so make a backup plan for it, let the user know the app can't connect to the server if there's no network. I'll say do push notifications, then if that fails try get from server manually and make local notifications, if the app can't make connection to the server fire up a local notification that says it couldn't connect to your server.

Hope this helps?