title: Call same service multiple times at the same time
body: <p>I have an <code>$http</code> service (or factory).</p>
  
  <pre><code>angular.module("app")
      .factory("PriceService", function ($http) {
          return {
              get: function (item) {
                  var url = "/pricing";
  
                  return $http.post(url, item);
              }
          }
      }); 
  </code></pre>
  
  <p>I am reading items from an Excel file. And each item will call the service once.</p>
  
  <pre><code>for (item in excelItems) {
      console.time(item.referenceId);
      PriceService.get(item).then(function(response) {
          console.timeEnd(item.referenceId);
          // process result
      }, function() {
          // error
      })
  }
  </code></pre>
  
  <p>The for loop finishes instantly, so all items should call <code>PriceService</code> almost at the same time. However, it seems that the items are calling the service one after another. Please see the console time results (the left column is refereceId).</p>
  
  <pre><code>    3: 2283.264ms
      5: 3167.943ms
      2: 3327.372ms
      11: 3767.073ms
      12: 3849.267ms
      14: 5388.853ms
      8: 15996.263ms
      16: 16636.952ms
      4: 17689.306ms
      18: 18190.733ms
      15: 19323.512ms
      20: 20009.020ms
      13: 23326.644ms
      10: 23378.259ms
      22: 24077.294ms
      24: 24568.147ms
      total: 24570.348ms
  </code></pre>
  
  <p>Is there any way that I can improve this? Thanks a lot!</p>