Choosing the right backend-as-a-service (BaaS) platform can make or break your project. After building production applications with both Supabase and Firebase, including InsureSignal which handles complex real-time insurance data, I have strong opinions on when to use each platform.

Let me break down everything you need to know to make an informed decision in 2025.

The Fundamental Difference: SQL vs NoSQL

The single most important distinction between Supabase and Firebase comes down to their database architecture:

Supabase uses PostgreSQL - a powerful relational database with full SQL support
Firebase uses Firestore - a NoSQL document database

This isn't just a technical detail. It fundamentally shapes how you model data, write queries, and scale your application.

When PostgreSQL (Supabase) Shines

-- Complex queries with joins are natural in Supabase
SELECT
  users.name,
  orders.total,
  products.name as product_name
FROM users
INNER JOIN orders ON users.id = orders.user_id
INNER JOIN order_items ON orders.id = order_items.order_id
INNER JOIN products ON order_items.product_id = products.id
WHERE orders.created_at > NOW() - INTERVAL '30 days'
ORDER BY orders.total DESC;

With Supabase, you get:

ACID compliance - Guaranteed data consistency
Complex joins - Query related data efficiently
SQL familiarity - Most developers already know SQL
Foreign keys - Enforce referential integrity at the database level
Advanced indexing - Full-text search, GIN indexes, partial indexes

When Firestore (Firebase) Shines

// Firestore's document model is great for hierarchical data
const userRef = doc(db, 'users', userId);
const userSnap = await getDoc(userRef);

// Subcollections keep related data organized
const ordersRef = collection(db, 'users', userId, 'orders');
const ordersSnap = await getDocs(ordersRef);

Firebase excels when:

Data is naturally hierarchical (nested documents)
You need offline-first mobile apps
Simple read patterns dominate (no complex joins)
You're already in the Google Cloud ecosystem

Setting Up: Developer Experience Compared

Supabase Initialization

// supabaseClient.ts
import { createClient } from '@supabase/supabase-js';

const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!;
const supabaseAnonKey = process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!;

export const supabase = createClient(supabaseUrl, supabaseAnonKey);

// Type-safe queries with generated types
import { Database } from '@/types/supabase';

const { data: users, error } = await supabase
  .from('users')
  .select('id, name, email, created_at')
  .eq('active', true)
  .order('created_at', { ascending: false });

Firebase Initialization

// firebaseClient.ts
import { initializeApp } from 'firebase/app';
import { getFirestore } from 'firebase/firestore';
import { getAuth } from 'firebase/auth';

const firebaseConfig = {
  apiKey: process.env.NEXT_PUBLIC_FIREBASE_API_KEY,
  authDomain: process.env.NEXT_PUBLIC_FIREBASE_AUTH_DOMAIN,
  projectId: process.env.NEXT_PUBLIC_FIREBASE_PROJECT_ID,
  storageBucket: process.env.NEXT_PUBLIC_FIREBASE_STORAGE_BUCKET,
  messagingSenderId: process.env.NEXT_PUBLIC_FIREBASE_MESSAGING_SENDER_ID,
  appId: process.env.NEXT_PUBLIC_FIREBASE_APP_ID,
};

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

Both setups are straightforward, but Supabase has fewer configuration options to manage.

Authentication: A Detailed Comparison

Supabase Auth

// Email/Password signup
const { data, error } = await supabase.auth.signUp({
  email: 'user@example.com',
  password: 'secure-password',
  options: {
    data: {
      full_name: 'John Doe',
      avatar_url: 'https://example.com/avatar.jpg',
    },
  },
});

// OAuth providers
const { data, error } = await supabase.auth.signInWithOAuth({
  provider: 'google',
  options: {
    redirectTo: 'https://yourapp.com/auth/callback',
  },
});

// Magic link (passwordless)
const { data, error } = await supabase.auth.signInWithOtp({
  email: 'user@example.com',
});

// Row Level Security integration
// In your Supabase dashboard SQL editor:
CREATE POLICY "Users can only view their own data"
ON users
FOR SELECT
USING (auth.uid() = id);

Supabase's killer feature is Row Level Security (RLS). Your security policies live in the database itself, not scattered across application code.

Firebase Auth

// Email/Password signup
import { createUserWithEmailAndPassword, updateProfile } from 'firebase/auth';

const userCredential = await createUserWithEmailAndPassword(
  auth,
  'user@example.com',
  'secure-password'
);

await updateProfile(userCredential.user, {
  displayName: 'John Doe',
  photoURL: 'https://example.com/avatar.jpg',
});

// OAuth providers
import { GoogleAuthProvider, signInWithPopup } from 'firebase/auth';

const provider = new GoogleAuthProvider();
const result = await signInWithPopup(auth, provider);

// Security rules (in firestore.rules file)
rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
    match /users/{userId} {
      allow read, write: if request.auth != null && request.auth.uid == userId;
    }
  }
}

Firebase Auth is more mature with features like phone authentication, anonymous auth, and multi-factor authentication built-in. However, security rules are separate from your data model.

Real-Time Capabilities

Both platforms excel at real-time data, but implementation differs significantly.

Supabase Real-Time

// Subscribe to database changes
const channel = supabase
  .channel('public:messages')
  .on(
    'postgres_changes',
    {
      event: '*', // INSERT, UPDATE, DELETE
      schema: 'public',
      table: 'messages',
      filter: 'room_id=eq.123',
    },
    (payload) => {
      console.log('Change received:', payload);
      // payload.new contains the new record
      // payload.old contains the previous record (for UPDATE/DELETE)
    }
  )
  .subscribe();

// Presence (who's online)
const presenceChannel = supabase.channel('room:123');

presenceChannel
  .on('presence', { event: 'sync' }, () => {
    const state = presenceChannel.presenceState();
    console.log('Online users:', state);
  })
  .subscribe(async (status) => {
    if (status === 'SUBSCRIBED') {
      await presenceChannel.track({
        user_id: user.id,
        online_at: new Date().toISOString(),
      });
    }
  });

Firebase Real-Time

import { onSnapshot, query, where, orderBy } from 'firebase/firestore';

// Real-time listener
const q = query(
  collection(db, 'messages'),
  where('roomId', '==', '123'),
  orderBy('createdAt', 'desc')
);

const unsubscribe = onSnapshot(q, (snapshot) => {
  snapshot.docChanges().forEach((change) => {
    if (change.type === 'added') {
      console.log('New message:', change.doc.data());
    }
    if (change.type === 'modified') {
      console.log('Modified message:', change.doc.data());
    }
    if (change.type === 'removed') {
      console.log('Removed message:', change.doc.data());
    }
  });
});

Firebase's real-time is slightly more mature and handles offline scenarios better. Supabase's implementation is catching up quickly and benefits from PostgreSQL's LISTEN/NOTIFY under the hood.

Pricing: The Real Numbers

Supabase Pricing (2025)

| Tier | Database | Auth Users | Storage | Price | |------|----------|------------|---------|-------| | Free | 500MB | Unlimited | 1GB | $0 | | Pro | 8GB | Unlimited | 100GB | $25/mo | | Team | 8GB | Unlimited | 100GB | $599/mo | | Enterprise | Custom | Unlimited | Custom | Custom |

Firebase Pricing (2025)

Firebase uses pay-as-you-go pricing which can be unpredictable:

Firestore reads: $0.036 per 100,000
Firestore writes: $0.108 per 100,000
Firestore deletes: $0.012 per 100,000
Storage: $0.026 per GB
Auth: Free up to 50,000 MAU

Real-world example: A medium-traffic app with 10,000 daily users doing 50 reads each would cost roughly:

10,000 x 50 x 30 = 15,000,000 reads/month
15,000,000 / 100,000 x $0.036 = $5.40/month just for reads

Supabase's predictable pricing is a major advantage for budgeting.

When to Choose Supabase

Choose Supabase when:

You need complex queries - Joins, aggregations, window functions
Data integrity matters - Foreign keys, constraints, transactions
You know SQL - Leverage existing knowledge
Predictable pricing - Fixed monthly costs
Open source matters - You can self-host Supabase
PostgreSQL extensions - PostGIS for geospatial, pg_vector for AI embeddings

// Example: Complex analytics query in Supabase
const { data: analytics } = await supabase
  .rpc('get_user_analytics', {
    start_date: '2025-01-01',
    end_date: '2025-12-31',
  });

// The function in PostgreSQL:
CREATE OR REPLACE FUNCTION get_user_analytics(start_date DATE, end_date DATE)
RETURNS TABLE (
  month TEXT,
  total_users BIGINT,
  active_users BIGINT,
  revenue DECIMAL
) AS $$
BEGIN
  RETURN QUERY
  SELECT
    TO_CHAR(DATE_TRUNC('month', created_at), 'YYYY-MM') as month,
    COUNT(DISTINCT id) as total_users,
    COUNT(DISTINCT CASE WHEN last_active > NOW() - INTERVAL '30 days' THEN id END) as active_users,
    SUM(lifetime_value) as revenue
  FROM users
  WHERE created_at BETWEEN start_date AND end_date
  GROUP BY DATE_TRUNC('month', created_at)
  ORDER BY month;
END;
$$ LANGUAGE plpgsql;

When to Choose Firebase

Choose Firebase when:

Mobile-first development - Excellent React Native/Flutter SDKs
Offline-first requirements - Built-in offline persistence
Hierarchical data - Nested documents fit your model
Google Cloud integration - Already using GCP services
Mature ecosystem - Cloud Functions, Hosting, ML Kit, etc.
Phone authentication - Native phone auth is seamless

// Firebase's offline persistence is automatic
import { enableIndexedDbPersistence } from 'firebase/firestore';

// Enable offline persistence
enableIndexedDbPersistence(db).catch((err) => {
  if (err.code === 'failed-precondition') {
    // Multiple tabs open
  } else if (err.code === 'unimplemented') {
    // Browser doesn't support
  }
});

// Your queries work offline automatically
const q = query(collection(db, 'todos'), where('userId', '==', currentUser.uid));
const snapshot = await getDocs(q); // Works offline!

Migration Considerations

If you're migrating between platforms, here are key considerations:

Firebase to Supabase

// Export Firestore data to JSON, then import to Supabase
// 1. Export from Firebase
const exportData = async () => {
  const usersSnap = await getDocs(collection(db, 'users'));
  const users = usersSnap.docs.map(doc => ({
    id: doc.id,
    ...doc.data(),
  }));
  return users;
};

// 2. Import to Supabase
const importData = async (users: any[]) => {
  const { error } = await supabase.from('users').insert(users);
  if (error) console.error('Import failed:', error);
};

Supabase to Firebase

// Export from Supabase
const { data: users } = await supabase.from('users').select('*');

// Import to Firestore
const batch = writeBatch(db);
users.forEach((user) => {
  const docRef = doc(db, 'users', user.id);
  batch.set(docRef, user);
});
await batch.commit();

My Recommendation

For most modern web applications in 2025, I recommend Supabase. Here's why:

SQL is a superpower - The flexibility of PostgreSQL queries is unmatched
Row Level Security - Security at the database level is more robust
Predictable costs - No surprise bills from read-heavy operations
Open source - No vendor lock-in, self-hosting is an option
Growing ecosystem - Edge functions, vector embeddings, and more

That said, Firebase remains excellent for mobile apps requiring robust offline support and when you're deeply integrated with Google Cloud.

For more backend architecture decisions and implementation guides, check out my posts on Prisma ORM and building fintech applications.

The best choice depends on your specific needs. Start with a small prototype on both platforms if you're unsure - both offer generous free tiers to experiment with.