title: How to firebase AB test new user onboarding?
body: <p>As some other questions pointed out if you're setting up a Remote Config based AB test there's no activation event based on user first opened.</p>
  <p>We want to AB test our new onboarding flow against the previous onboarding experience however without a startup trigger we're not sure how to properly create this experiment.</p>
  <p>One <a href="https://stackoverflow.com/q/47453889/740474">SO answer</a> talks about sending a custom activation event with a timestamp and then filtering the test participants by that timestamp e.g. <code>custom_first_open</code> &gt; 1234567... however the onboarding flow is the first thing the user is to see.</p>
  <p>From my understanding as soon as the user initializes their remote config they will be subscribed to any active experiments. We would have to send the custom event before initialization and it would have to be immediately available to the AB test. AB test data and Firebase events both seem to be very slow to register (hours to days) so I doubt it would properly configure the user for the onboarding test using this trick.</p>
  <p>Is there another way to use AB testing to test onboarding efficacy only against new users?</p>