title: Do I need to use MemeCache for authentication?
body: <p>I am developing a chat app in which I am using firestore, functions &amp; Cloud message. I planned to reduce cost to minimum if possible.</p>
  <p>One thing I found that whenever user will send message or ask to receive message, He must need to be authenticated first. User can be verified using token that he will get after login. I save that token in firestore document. But, While we authenticate Firestore counts one read in the document for every message sent. So I am thinking to add Memory Store to it if it is possible. But Please tell me is it going to be wise decision or any cons.</p>
  <p>You can also suggest me some innovative ways or some threads/articles related to this.
  Thank You.</p>