Cloud Functions setup in Firebase - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

Cloud Function Trigger Behavior

You deploy a Firebase Cloud Function triggered by Firestore document creation in the 'orders' collection. What happens when a new document is added to 'orders'?

A The function runs continuously as long as there is at least one document in 'orders'.

B The function runs once for every update to any document in 'orders'.

C The function runs only once when the first document is added to 'orders'.

D The function runs once for each new document added to 'orders'.

💡 Hint

Think about what triggers a Firestore onCreate function.

The Cloud Function triggers every time a new document is created in the specified collection. It does not trigger on updates or deletions.

❓ Configuration

intermediate

Correct Firebase Function Initialization

Which code snippet correctly initializes a Firebase Cloud Function to respond to HTTP requests?

A

const functions = require('firebase-functions');
exports.myFunc = functions.https.onRequest((req, res) => { res.send('Hello'); });

B

const functions = require('firebase-functions');
exports.myFunc = functions.firestore.document('path').onWrite((change, context) => { /* ... */ });

C

const functions = require('firebase-functions');
exports.myFunc = functions.database.ref('path').onWrite((change, context) => { /* ... */ });

D

const functions = require('firebase-functions');
exports.myFunc = functions.storage.object().onFinalize((object) => { /* ... */ });

💡 Hint

Check which Firebase function type supports HTTP triggers.

Only functions.https.onRequest creates an HTTP-triggered function. Others are for database or storage triggers.

❓ Architecture

advanced

Designing Scalable Cloud Functions

You want to design a Firebase Cloud Function that processes image uploads to Cloud Storage and scales efficiently under heavy load. Which approach is best?

A Use a Cloud Function triggered on image upload that places a message in a Pub/Sub queue for asynchronous processing.

B Use a single Cloud Function triggered on every image upload that processes the image synchronously.

C Use a Cloud Function triggered on HTTP requests to process images uploaded manually by users.

D Use a Cloud Function triggered on Firestore writes to track image uploads and process images in the function.

💡 Hint

Think about decoupling processing from upload to handle spikes.

Using Pub/Sub decouples upload from processing, allowing the system to scale and retry processing without blocking uploads.

❓ security

advanced

Securing Firebase Cloud Functions

Which practice best secures a Firebase Cloud Function that handles sensitive user data via HTTP requests?

A Use HTTP Basic Authentication with hardcoded credentials in the function.

B Allow all requests and rely on Firestore security rules to protect data.

C Require Firebase Authentication tokens and verify them inside the function before processing.

D Make the function public and encrypt data only after processing.

💡 Hint

Think about verifying the identity of the caller before processing sensitive data.

Verifying Firebase Authentication tokens ensures only authorized users access the function, protecting sensitive data.

✅ Best Practice

expert

Optimizing Cold Start Times in Cloud Functions

You notice your Firebase Cloud Functions have high cold start latency. Which option is the best way to reduce cold start times?

A Increase the memory allocation to the maximum allowed for all functions.

B Keep function code minimal and avoid importing large libraries unless needed.

C Deploy all functions in a single file to reduce deployment size.

D Use synchronous blocking code to ensure all initialization completes before handling requests.

💡 Hint

Think about what affects the time it takes to start a function instance.

Smaller code and fewer imports reduce initialization time, lowering cold start latency.