title: Does Azure Function App run several instances at the same time?
body: <p>If I have a Function app like so</p>
  
  <pre><code>   public static class Function1
      {
          private static readonly HttpClient httpClient = new HttpClient();
  
          [FunctionName("SomeRandomFunction")]
          public static async Task&lt;IActionResult&gt; Run([HttpTrigger(AuthorizationLevel.Anonymous, "get", "post", Route = null)] HttpRequest req, ILogger log)
          {
              ulong i = 0;
              Thread.Sleep(10000);
              return (ActionResult)new OkObjectResult($"Hello thread Finished.");
          }
  }
  </code></pre>
  
  <p>Are different instances of the function created if different e.g. mobile devices trigger the function at the same time? </p>
  
  <p>I had inferred this from this <a href="https://docs.microsoft.com/en-us/azure/azure-functions/functions-scale" rel="nofollow noreferrer">quote</a> "When you're using the Premium plan, instances of the Azure Functions host are added and removed based on the number of incoming events just like the Consumption plan". I'm on S1 plan. </p>
  
  <p>However when I tested a thread.sleep in function "SomeRandomFunction" like above with two calls for this same function from two different private browser windows, the second call only starts when the first one finished. Why does this happen if it's possible to create several instances of the same function app?</p>
  
  <p>Or is a multi-threading implementation required to have several instances running at the same time?</p>
  
  <p>Thank you</p>