Facebook sign-in in Firebase - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Facebook Sign-In Flow in Firebase

Which step correctly describes the initial action when implementing Facebook sign-in using Firebase Authentication?

A Directly call Firebase signInWithPopup without initializing Facebook SDK separately.

B Initialize the Facebook SDK and then use Firebase to handle the authentication token.

C Use Firebase Admin SDK to authenticate Facebook users on the client side.

D Create a custom OAuth server to handle Facebook tokens before Firebase authentication.

💡 Hint

Think about how Firebase and Facebook SDKs work together for sign-in.

Firebase Authentication can directly handle Facebook sign-in using signInWithPopup or signInWithRedirect without separately initializing the Facebook SDK.

❓ Configuration

intermediate

Configuring Facebook Sign-In in Firebase Console

Which configuration step is mandatory in the Firebase Console to enable Facebook sign-in?

A Enable Facebook sign-in in Firebase Realtime Database rules.

B Upload the Facebook SDK files to Firebase Hosting.

C Add the Facebook App ID and App Secret in the Firebase Authentication providers section.

D Set up a Firebase Cloud Function to handle Facebook OAuth callbacks.

💡 Hint

Think about what Firebase needs to communicate with Facebook.

Firebase needs the Facebook App ID and App Secret to connect and verify users via Facebook OAuth.

❓ service_behavior

advanced

Handling Token Expiry in Facebook Sign-In with Firebase

What happens if a Facebook access token used for Firebase sign-in expires, and the user tries to sign in again without refreshing the token?

A Firebase automatically refreshes the Facebook token and signs the user in.

B Firebase sign-in fails with an error indicating invalid or expired credential.

C Firebase signs in the user but with limited permissions until token refresh.

D Firebase ignores the token expiry and signs in the user normally.

💡 Hint

Consider how Firebase treats expired OAuth tokens.

Firebase requires a valid Facebook access token; if expired, sign-in fails and an error is returned.

❓ security

advanced

Securing Facebook Sign-In with Firebase

Which practice best improves security when implementing Facebook sign-in with Firebase?

A Disable Firebase Authentication email/password sign-in to force Facebook-only sign-in.

B Store the Facebook App Secret in the client-side code for easy access.

C Use Firebase Realtime Database rules to allow all authenticated users full read/write access.

D Verify the Facebook access token on your backend server before passing it to Firebase Authentication.

💡 Hint

Think about protecting sensitive credentials and validating tokens.

Verifying tokens on the backend prevents token forgery and protects your app from unauthorized access.

❓ Architecture

expert

Designing a Scalable Facebook Sign-In System with Firebase

You want to design a system that supports millions of users signing in with Facebook using Firebase Authentication. Which architectural choice best supports scalability and reliability?

A Use Firebase Authentication with Facebook sign-in on the client side, and implement Cloud Functions to handle user data processing asynchronously.

B Store all Facebook access tokens in Firestore and validate them on every user request.

C Use Firebase Authentication only for email/password and handle Facebook sign-in entirely on your backend server.

D Build a custom OAuth server to handle Facebook sign-in and then sync users to Firebase Authentication manually.

💡 Hint

Consider Firebase's managed services and asynchronous processing for scale.

Using Firebase Authentication client-side with Cloud Functions for backend processing leverages Firebase's scalability and reduces server load.