A lot of teams love Firebase Authentication because it solves the hardest pieces of user identity passwords, OAuth, tokens, verification without needing to build those systems yourself. At the same time, many developers prefer MongoDB for storing application data because it’s flexible, scalable, and handles complex data models really well. The good part? You don’t have to choose one or the other. You can use Firebase Auth to handle identity and MongoDB to store your app data, and they integrate surprisingly well. Your frontend signs in the user → Firebase issues a secure ID token → your backend verifies it → and MongoDB handles all data operations. It’s a simple setup that gives you the reliability of Firebase Auth and the power of MongoDB in the same stack perfect for building modern, scalable applications.