title: Cloud Functions: where to keep access token for API calls
body: <p>I have created a <strong>Cloud Function</strong> which:</p>
  
  <ol>
  <li>Receives some data</li>
  <li>Calls a google API to verify the data are correct</li>
  </ol>
  
  <p>Now, to call the google API I need to authenticate first. This will give me an access token (that expires) that can be used for subsequent calls.</p>
  
  <p>I'm wondering <strong>where can I save this access token</strong> so that other invocations of the function can "see" it and use it. I know I cannot use a "global variable" as the function may run on different machines.</p>
  
  <p>The obvious solution is to write it in Realtime Database... But I don't really like it, as someone could get access to it... Does Cloud Functions provide an object or something where I can write data into?</p>