title: Subscription throttling limit
body: <p>I tried to make multiple subscriptions to a single user, to test out how many subscription requests i can send until throttling occurs. I used the following code:</p>
  
  <pre><code>for (int i = 0; i &lt; 10000; i++)
  {
        try
        {
              var request = graphClient.Subscriptions.Request();
  
              var result = await request.AddAsync(
              new Subscription
              {
                  ChangeType = "created,updated,deleted",
                  NotificationUrl = notificationUrl,
                  Resource = "/users/" + userId + "/" + resource,
                  ExpirationDateTime = DateTimeOffset.UtcNow.AddMinutes(4230),
                  ClientState = "my-subscription-identifier"
              }
              );
  
              AddOutputMessage((i + 1) + " Created Webhook", Color.Blue);
        }
        catch (ServiceException serviceException)
        {
             AddOutputErrorMessage(serviceException);
        }
  }
  </code></pre>
  
  <p>The throttling limit per user per app is 10000 in 10 minutes (as described in <a href="https://stackoverflow.com/questions/47654844/microsoft-graph-api-throttling">another stackoverflow post</a>). I already tested this limit by making some requests to a single users calendar and contacts where it seems to work. </p>
  
  <p>I was able to make 220 subscriptions until throttling occured (tested it three times). Even though that seems to be a little low, my end goal is to make multiple subscription requests for multiple users (for example 1000 subscriptions to a 1000 users), so it wouldn't be a problem if this throttling limit is for a single user only.</p>
  
  <p>The throttling (HttpStatusCode 429) service exception for the subscriptions request also contained the error code 'ExtensionError' which i couldn't really find in the <a href="https://developer.microsoft.com/en-us/graph/docs/concepts/errors" rel="nofollow noreferrer">doc</a>.<a href="https://i.stack.imgur.com/5IO4Z.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5IO4Z.png" alt="ExtensionError"></a></p>
  
  <p>What i want to know is:</p>
  
  <ul>
  <li>What are the throttling limits for the '/subscription endpoint'?</li>
  <li>Especially after how many requests does throttling occur? (per user and overall per app) e.g. if i want to make subscriptions to 1000 users will i be throttled after 220?</li>
  <li>What is an 'ExtensionError'?</li>
  </ul>