firebase-firestore

# Firebase Firestore Database

**Status**: Production Ready
**Last Updated**: 2026-01-25
**Dependencies**: None (standalone skill)
**Latest Versions**: firebase@12.8.0, firebase-admin@13.6.0

---

## Quick Start (5 Minutes)

### 1. Install Firebase SDK

```bash
# Client SDK (web/mobile)
npm install firebase

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

### 2. Initialize Firebase (Client)

```typescript
// 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)

```typescript
// 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+)

```typescript
import {
  collection,
  doc,
  addDoc,
  getDoc,
  getDocs,
  setDoc,
  updateDoc,
  deleteDoc,
  query,
  where,
  orderBy,
  limit,
  serverTimestamp,
  Timestamp,
} from 'firebase/firesto