title: AWS API Gateway authorizer google sign in
body: <p>I have an API Gateway/lambda REST API that is being accessed from a react web app. I need to add authentication using google as an identity provider. The app should also keep the user signed in.</p>
  
  <p>I understand when the user first grants access to the (react) client app, it should send the ID token to my backend, which should then verify the token.</p>
  
  <p>Since my architecture is serverless, I assume the verifying should be done in the API Gateway authorizer function, which then grants access to the API on successful verification of the token.</p>
  
  <p>My question is, how do I then create a persistent session? Should I be saving anything to my database about the user? Does the token need to be verified on every API call?</p>
  
  <p>Should the authorizer be checking if the user is already registered or if it's a new user?</p>