title: Upgrading AngularJS app to an hybrid Angular-1.6 / Angular-4 kills the perf
body: <p>I've just updated my AngularJS 1.6 app by following the <a href="https://angular.io/docs/ts/latest/guide/upgrade.html" rel="noreferrer">Angular 4 upgrade guide</a>. Basically I've added new angular 4 dependencies in <code>package.json</code>, bootstrapped the app via <code>UpgradeModule</code> and created a new simple component in angular 4. Everything works as expected but the performance is really bad! </p>
  
  <p>The application is a dashboard application with potentially lots of widget components and lots of http requests to the backend to fill each widget content.</p>
  
  <p>Depending on the dashboard, the upgraded app is 2x to 5x slower to load and display the dashboard, and chrome network console shows the http requests are run in a sequence instead of being shot all at once like in the 1.6 version. Overall, the UI is also a lot less fluid.</p>
  
  <p>I've played with <code>ngZone</code> and tried to run requests outside of angular <code>zone.runOutsideAngular(() =&gt; { ... })</code> to reduce refresh cost due to change detection. The result is slightly faster but still far slower than the original 1.6 only version.</p>
  
  <p>Is there something to consider when upgrading to an hybrid 1.6-4 app to keep great original performance? Thanks!</p>