title: Firebase - best practice for session_start and user_engagement
body: <p>I just started to work with Firebase events.
  And I see a lot of garbage in data:</p>
  <ol>
  <li>I see &quot;interactions&quot; with <code>os_update</code> or <code>app_update</code> events with nothing more, so there is not actually a &quot;session&quot;, but <code>session_start</code> is also sent.</li>
  </ol>
  <p>Example:</p>
  <pre><code>app_update 12:00:01 
  session_start 12:00:02 
  session_start 13:00:05
  </code></pre>
  <p>So I can't count &quot;clean&quot; metrics, for example - average sessions per user per week, because there is such garbage.</p>
  <ol start="2">
  <li>There are also &quot;sessions&quot; with only <code>session_start</code> event.</li>
  </ol>
  <p>So, what I'm thinking:</p>
  <ol>
  <li><p>I can't find to set minimum session duration, <code>setMinimumSessionDuration()</code> method is obsolete.</p>
  </li>
  <li><p>If I find a way to set minimum duration to 5sec
  There will be strange behavior, for example:</p>
  </li>
  </ol>
  <hr />
  <pre><code>screen_view 12:00:01
  session_start 12:00:04
  </code></pre>
  <p>It's strange that session start is after event and will be a loss of data, if user quit before session_start but have <code>screen_view</code>.
  Maybe it's okay to cut the garbage.</p>
  <ol start="3">
  <li>If we set minimum duration to 5sec, to obviously we need to set minimum duration for firing <code>user_engagement</code> event, because it will be very strange to see <code>user_engagement</code> before session_start ot without session_start. So I think we should set minimum duration for user engagement like 10sec or 30sec.</li>
  </ol>
  <p>So, how did you solved this problems?
  Any tips and tricks, what is the best practice?
  Thanks.</p>