Firebase Firestore Database

Status: Production Ready Last Updated: 2026-01-25 Dependencies: None (standalone skill) Latest Versions: [email protected], [email protected]

Quick Start (5 Minutes)

1. Install Firebase SDK

# Client SDK (web/mobile)
npm install firebase

# Admin SDK (server/backend)
npm install firebase-admin

2. Initialize Firebase (Client)

// src/lib/firebase.ts
import { initializeApp } from 'firebase/app';
import { getFirestore } from 'firebase/firestore';

const firebaseConfig = {
  apiKey: process.env.FIREBASE_API_KEY,
  authDomain: process.env.FIREBASE_AUTH_DOMAIN,
  projectId: process.env.FIREBASE_PROJECT_ID,
  storageBucket: process.env.FIREBASE_STORAGE_BUCKET,
  messagingSenderId: process.env.FIREBASE_MESSAGING_SENDER_ID,
  appId: process.env.FIREBASE_APP_ID,
};

const app = initializeApp(firebaseConfig);
export const db = getFirestore(app);

3. Initialize Firebase Admin (Server)

// src/lib/firebase-admin.ts
import { initializeApp, cert, getApps } from 'firebase-admin/app';
import { getFirestore } from 'firebase-admin/firestore';

// Initialize only once
if (!getApps().length) {
  initializeApp({
    credential: cert({
      projectId: process.env.FIREBASE_PROJECT_ID,
      clientEmail: process.env.FIREBASE_CLIENT_EMAIL,
      // Replace escaped newlines in private key
      privateKey: process.env.FIREBASE_PRIVATE_KEY?.replace(/\\n/g, '\n'),
    }),
  });
}

export const adminDb = getFirestore();

CRITICAL:

• Never expose FIREBASE_PRIVATE_KEY in client code
• Use Admin SDK for server-side operations (bypasses security rules)
• Use Client SDK for authenticated user operations

Core Operations

Document CRUD (Client SDK - Modular v9+)

import {
  collection,
  doc,
  addDoc,
  getDoc,
  getDocs,
  setDoc,
  updateDoc,
  deleteDoc,
  query,
  where,
  orderBy,
  limit,
  serverTimestamp,
  Timestamp,
} from 'firebase/firestore';
import { db } from './firebase';

// CREATE - Auto-generated ID
const docRef = await addDoc(collection(db, 'users'), {
  name: 'John Doe',
  email: '[email protected]',
  createdAt: serverTimestamp(),
});
console.log('Created document with ID:', docRef.id);

// CREATE - Specific ID
await setDoc(doc(db, 'users', 'user-123'), {
  name: 'Jane Doe',
  email: '[email protected]',
  createdAt: serverTimestamp(),
});

// READ - Single document
const docSnap = await getDoc(doc(db, 'users', 'user-123'));
if (docSnap.exists()) {
  console.log('Document data:', docSnap.data());
} else {
  console.log('No such document!');
}

// READ - Collection with query
const q = query(
  collection(db, 'users'),
  where('email', '==', '[email protected]'),
  orderBy('createdAt', 'desc'),
  limit(10)
);
const querySnapshot = await getDocs(q);
querySnapshot.forEach((doc) => {
  console.log(doc.id, ' => ', doc.data());
});

// UPDATE - Merge fields (doesn't overwrite entire document)
await updateDoc(doc(db, 'users', 'user-123'), {
  name: 'Jane Smith',
  updatedAt: serverTimestamp(),
});

// UPDATE - Set with merge (creates if doesn't exist)
await setDoc(doc(db, 'users', 'user-123'), {
  lastLogin: serverTimestamp(),
}, { merge: true });

// DELETE
await deleteDoc(doc(db, 'users', 'user-123'));

Document CRUD (Admin SDK)

import { adminDb } from './firebase-admin';
import { FieldValue, Timestamp } from 'firebase-admin/firestore';

// CREATE
const docRef = await adminDb.collection('users').add({
  name: 'John Doe',
  createdAt: FieldValue.serverTimestamp(),