Add OAuth 2.0 to a Node.js CRUD app` is a tutorial that guides developers through the process of adding OAuth 2.0 authentication to a Node.js CRUD application using the ngrok JavaScript SDK. The tutorial assumes prior knowledge of Node.js, Express.js, and React.js, but can be followed independently by new developers. To add OAuth functionality, the code must first serve the React frontend from the same Node process running the backend, then use the ngrok JavaScript SDK to define ingress directly inside the application, choosing a static domain for stability. The tutorial demonstrates how to secure the application with Google's OAuth implementation, allowing users to authenticate and authorizing their access to the application. Finally, the code includes a graceful kill switch to ensure clean exit in case of an interruption.