title: What is needed to use Cloud Firestore from Google App Engine Standard Environment
body: <p>I read many GCP documents relating to credentials for using Cloud Firestore from Google App Engine Standard Environment, but I'm very confused now. </p>
  
  <p>According to the following pages, I assume there can be two service accounts from Google App Engine and Firebase. So there are two credentials from each of them, right?</p>
  
  <p><a href="https://firebase.google.com/docs/admin/setup#initialize_the_sdk" rel="nofollow noreferrer">https://firebase.google.com/docs/admin/setup#initialize_the_sdk</a>
  <a href="https://cloud.google.com/docs/authentication/production" rel="nofollow noreferrer">https://cloud.google.com/docs/authentication/production</a></p>
  
  <p>The documentation recommends to use the environment variable for a credential like the following,</p>
  
  <pre><code>export GOOGLE_APPLICATION_CREDENTIALS="[PATH]"
  </code></pre>
  
  <p>but which credential should I use in my case?</p>