title: Azure notification hubs + APNS result in missed topic notifications. Must I archive all sent notifications for iOS devices?
body: <p>Azure notification hubs have a feature that allow for subscribing to various topics in a many to many relationship. (many devices to many declared topic strings)</p>
  
  <p>Suppose I take these steps:</p>
  
  <ol>
  <li>I send an iOS device a notification, "test 1".  </li>
  <li>The device goes offline. </li>
  <li>I send "test 2"</li>
  <li>I send "test 3". </li>
  <li>The device comes back online.  </li>
  <li>APNS only sends "test 3". Test 2 was dropped</li>
  </ol>
  
  <p>Not to mention that APNS will only notify the most recent event "Test 3", it can also drop additional alerts in iOS 11 if I exceed the 30 maximum per day.</p>
  
  <p>One of the things I like about Azure Hub service, is that I can manage that subscription "state" in an external storage. Now however, it seems I have to track the subscriptions myself, rebuilding part of the Azure HUB architecture... archiving out the subscriptions, topics, etc so the device can query the server for all missing events. </p>
  
  <p><strong>Question</strong> </p>
  
  <ul>
  <li>How do I reconcile the features of Azure Hub and topic subscription with the issue of dropped APNS pushes?</li>
  </ul>