Realtime Database vs Firestore decision in Firebase - Quick Revision & Key Differences

Recall & Review

beginner

What is Firebase Realtime Database?

Firebase Realtime Database is a cloud-hosted NoSQL database that stores data as one large JSON tree and syncs data in real-time to connected clients.

beginner

What is Firestore in Firebase?

Firestore is a flexible, scalable NoSQL database that stores data in documents organized into collections, supporting richer queries and offline support.

intermediate

Which Firebase database is better for complex queries and why?

Firestore is better for complex queries because it supports indexed queries, compound queries, and more advanced filtering compared to Realtime Database.

intermediate

When should you choose Realtime Database over Firestore?

Choose Realtime Database if you need simple data syncing with low latency and your data structure is simple, like a single JSON tree.

beginner

What is a key difference in data structure between Realtime Database and Firestore?

Realtime Database stores data as one large JSON tree, while Firestore stores data in documents grouped into collections, allowing more structured data.

Which Firebase database supports offline data persistence by default?

A Neither

B Realtime Database

C Both

D Firestore

Firestore supports offline data persistence by default on mobile and web clients, allowing apps to work offline seamlessly.

Which database uses a JSON tree to store data?

A Realtime Database

B Firestore

C Both

D None

Realtime Database stores data as one large JSON tree, making it simple but less structured.

For which scenario is Firestore more suitable?

A Simple, flat data with real-time syncing

B Complex queries and structured data

C Only offline data storage

D Storing files and images

Firestore supports complex queries and structured data with documents and collections.

Which database generally has lower latency for simple real-time updates?

A Realtime Database

B Firestore

C Both have the same latency

D Depends on the network only

Realtime Database is optimized for low-latency real-time syncing of simple data.

Which Firebase database supports automatic scaling better for large datasets?

A Realtime Database

B Both equally

C Firestore

D Neither

Firestore is designed to scale automatically for large datasets and high traffic.

Explain the main differences between Firebase Realtime Database and Firestore.

Think about how data is stored and how you might query it.

Describe a scenario where you would choose Realtime Database over Firestore and why.

Imagine a chat app with simple messages.

Practice

1. Which Firebase database is best suited for simple real-time syncing of data as a JSON tree?

easy

A. Realtime Database

B. Firestore

C. Cloud Storage

D. Firebase Hosting

Solution

1. Step 1: Understand data structure of Realtime Database

   Realtime Database stores data as a JSON tree, which is simple and fast for syncing.

2. Step 2: Compare with Firestore

   Firestore uses collections and documents, better for complex queries but not just simple JSON tree syncing.

3. Final Answer:

   Realtime Database -> Option A

4. Quick Check:

   Simple JSON tree sync = Realtime Database [OK]

Hint: Simple JSON tree and fast sync? Choose Realtime Database [OK]

Common Mistakes:

• Confusing Firestore with Realtime Database
• Choosing Cloud Storage for database needs
• Thinking Firebase Hosting stores data

2. Which syntax correctly references a document in Firestore?

easy

A. db.store('users').document('user1')

B. db.collection('users').doc('user1')

C. db.get('users/user1')

D. db.ref('users/user1')

Solution

1. Step 1: Recall Firestore document reference syntax

   Firestore uses collection().doc() to reference documents.

2. Step 2: Identify incorrect options

   db.ref() is Realtime Database syntax; db.get() and db.store() are invalid here.

3. Final Answer:

   db.collection('users').doc('user1') -> Option B

4. Quick Check:

   Firestore document ref = collection().doc() [OK]

Hint: Firestore uses collection().doc() syntax [OK]

Common Mistakes:

• Using Realtime Database syntax for Firestore
• Mixing method names like get() or store()
• Confusing document and collection references

3. Given this Firestore query code, what will be the output if the 'users' collection has documents with ages 20, 25, and 30?

db.collection('users').where('age', '>', 22).get().then(snapshot => {
  let result = [];
  snapshot.forEach(doc => result.push(doc.data().age));
  console.log(result);
});

medium

A. [25, 30]

B. [20, 25, 30]

C. [22, 25]

D. []

Solution

1. Step 1: Understand the query condition

   The query filters users where age is greater than 22, so ages 25 and 30 qualify.

2. Step 2: Determine the output array

   The code collects ages from matching documents, so output is [25, 30].

3. Final Answer:

   [25, 30] -> Option A

4. Quick Check:

   age > 22 = [25, 30] [OK]

Hint: Filter > 22 excludes 20, includes 25 and 30 [OK]

Common Mistakes:

• Including 20 which is not > 22
• Confusing >= with > operator
• Assuming empty result without checking data

4. You wrote this Realtime Database code but it throws an error:

firebase.database().collection('users').doc('user1').get()

What is the main issue?

medium

A. Missing authentication before accessing database

B. The get() method is asynchronous and needs await

C. Realtime Database does not have collection() or doc() methods

D. The database URL is not specified

Solution

1. Step 1: Identify API mismatch

   Realtime Database uses ref() instead of collection() and doc(), which are Firestore methods.

2. Step 2: Confirm correct method usage

   Using collection() and doc() on Realtime Database causes error because those methods don't exist there.

3. Final Answer:

   Realtime Database does not have collection() or doc() methods -> Option C

4. Quick Check:

   Realtime DB uses ref(), not collection()/doc() [OK]

Hint: Realtime DB uses ref(), not collection() or doc() [OK]

Common Mistakes:

• Assuming get() needs await causes confusion
• Blaming authentication without checking API
• Thinking database URL causes this syntax error

5. You need to build a chat app that requires fast real-time updates and simple data structure. Which Firebase database should you choose and why?

hard

A. Firestore, because it supports complex queries and offline caching

B. Firestore, because it scales better for large datasets

C. Realtime Database, because it stores data in collections and documents

D. Realtime Database, because it syncs data instantly as a JSON tree

Solution

1. Step 1: Analyze app requirements

   The chat app needs fast real-time updates and a simple data structure.

2. Step 2: Match requirements to database features

   Realtime Database syncs data instantly as a JSON tree, ideal for simple real-time apps.

3. Step 3: Eliminate incorrect options

   Firestore supports complex queries and scales well but is more complex; Realtime Database does not use collections/documents.

4. Final Answer:

   Realtime Database, because it syncs data instantly as a JSON tree -> Option D

5. Quick Check:

   Simple real-time chat = Realtime Database [OK]

Hint: Fast real-time + simple data? Pick Realtime Database [OK]

Common Mistakes:

• Choosing Firestore for simple real-time needs
• Confusing data structure of Realtime Database
• Assuming Realtime Database uses collections/documents