title: Firebase Functions triggered by database change in my simple case
body: <p>In my firebase database, I have a "users" node.</p>
  
  <p>I use <strong>Firebase Functions</strong> for backend functions. My javascript code (node.js) running in <strong>Functions</strong> needs to do something when a new <code>user</code> is added to database, here is the backend function code:</p>
  
  <pre><code>    // required modules
      const functions = require('firebase-functions');
      const admin = require('firebase-admin');
  
      // my backend function
      exports.onUserCreated = functions.auth.user().onCreate(event =&gt; {
        // Do something when a new user is created
      }
  </code></pre>
  
  <p>I successfully deployed my backend function to firebase Functions.</p>
  
  <p>Then, I manually added a user under <code>users</code> node of firebase database. Then, I go to <strong>Firebase Functions</strong>, I see the <code>onUserCreated</code> Function listed there in console, but the number of executions is 0. </p>
  
  <p>What could be the reason why my function is not triggered when I manually added a user in database? </p>