Realtime Database vs Firestore: Key Differences and Usage Guide

Use Realtime Database when you need simple, low-latency syncing of small data sets with a flat data structure. Choose Firestore for more complex, scalable apps requiring richer queries, hierarchical data, and offline support.

Quick Comparison

This table summarizes the main differences between Realtime Database and Firestore to help you decide quickly.

Feature	Realtime Database	Firestore
Data Model	JSON tree (flat structure preferred)	Documents and collections (hierarchical)
Querying	Limited, shallow queries	Rich, indexed queries with filters and sorting
Offline Support	Basic offline support	Advanced offline support with automatic sync
Scalability	Best for small to medium apps	Designed for large, complex apps
Latency	Very low latency for simple sync	Low latency but slightly higher than Realtime Database
Pricing Model	Based on data downloaded and stored	Based on document reads, writes, and storage

Key Differences

Realtime Database stores data as one large JSON tree, which works well for simple data and quick syncing. It is optimized for low latency and real-time updates but has limited querying capabilities, making it harder to handle complex data relationships.

Firestore uses a document-based model with collections and documents, allowing nested data and more structured organization. It supports advanced queries with filters, sorting, and pagination, which makes it better for apps with complex data needs.

Offline support in Firestore is more robust, automatically syncing changes when the device reconnects. Firestore also scales better for large apps and has a more flexible pricing model based on operations, which can be more cost-effective depending on usage.

Code Comparison

Here is how you listen to real-time updates of a list of messages in Realtime Database using JavaScript.

javascript

import { getDatabase, ref, onValue } from "firebase/database";

const db = getDatabase();
const messagesRef = ref(db, 'messages');

onValue(messagesRef, (snapshot) => {
  const data = snapshot.val();
  console.log('Realtime DB messages:', data);
});

Output

Realtime DB messages: { message1: { text: 'Hello' }, message2: { text: 'Hi' } }

Firestore Equivalent

Here is how you listen to real-time updates of a list of messages in Firestore using JavaScript.

javascript

import { getFirestore, collection, onSnapshot } from "firebase/firestore";

const db = getFirestore();
const messagesCol = collection(db, 'messages');

onSnapshot(messagesCol, (snapshot) => {
  const messages = snapshot.docs.map(doc => ({ id: doc.id, ...doc.data() }));
  console.log('Firestore messages:', messages);
});

Output

Firestore messages: [ { id: 'message1', text: 'Hello' }, { id: 'message2', text: 'Hi' } ]

When to Use Which

Choose Realtime Database when your app needs very fast, simple syncing of small or flat data sets, such as chat apps or live feeds with minimal querying.

Choose Firestore when your app requires complex queries, hierarchical data, offline support, and scalability for larger or more feature-rich applications.

Firestore is generally recommended for new projects unless you have a specific need for the Realtime Database's simplicity and ultra-low latency.

Key Takeaways

Use Realtime Database for simple, low-latency syncing with flat data.

Use Firestore for complex queries, hierarchical data, and better offline support.

Firestore scales better and suits larger, feature-rich apps.

Realtime Database has simpler pricing but limited querying.

Firestore is recommended for most new projects unless simplicity is key.