Supabase vs Firebase vs PlanetScale: Real Database Costs
Your startup’s first database bill hits in week 4. You’ve built for 2,000 users, analytics are good, traffic is steady. Then Stripe sends the invoice: $847 for Firebase, $340 for Supabase, $210 for PlanetScale — same data, same load. You’ve just learned what most founders learn too late: database cost models are not created equal.
Picking Supabase, Firebase, or PlanetScale feels like a technical decision. It’s actually a financial one disguised as infrastructure. Here’s what each one actually costs.
Firebase: Brilliant but Expensive at Scale
Firebase is Google’s serverless database. You pay for operations: $0.06 per 100,000 reads, $0.18 per 100,000 writes plus storage and network. The math seems gentle at launch.
But here’s the trap: every operation counts. A page load that reads 5 documents = 5 billable reads. A background job that syncs user data every minute = 1,440 reads per user per day. With 1,000 active users, that’s 1.44M reads daily. At $0.06 per 100k, that’s roughly $26/day, or $780/month — before you’ve written a single paid feature.
Real example: for semi-realistic workloads (10k DAU, moderate queries), expect $800–$3,000/month.
Firebase’s advantages: real-time APIs, auth bundled in, blazing-fast global CDN, zero ops. Its cost trade-off: you pay for every byte you touch.
Supabase: PostgreSQL Without the Headache
Supabase is PostgreSQL hosted + real-time APIs + auth. Fixed pricing: $25/month starter (500MB storage, unlimited API calls) to $550/month pro (100GB storage).
The key difference: unlimited API calls. Once you’re paying for the tier, you’re not paying again when your analytics job hammers the database at 2 AM.
For the same 1,000-user app with 1.44M daily reads, Supabase costs you the tier price — let’s say $100/month (includes the reads in the bundle). Firebase would cost $780+. That’s a 7.8x difference.
Supabase’s trade-off: you’re inheriting PostgreSQL’s operational surface. You get full SQL, JSONB, window functions, custom types — brilliant for complex queries. But if your schema design is sloppy, you’ll pay in N+1 queries and slow joins, not billing surprises.
PlanetScale: Serverless MySQL
PlanetScale is Vitess-powered MySQL. $39/month starter (1 billion reads/month) to $299/month pro (50 billion reads/month) at 100% predictable cost.
This is a middle ground. You get a familiar SQL dialect, true serverless scaling (auto-shards your database horizontally), and a fixed bill. For the same 1,000-user app: 1.44M reads/day × 30 days = 43.2M reads/month. That fits comfortably in the $39 starter plan (1 billion reads included).
PlanetScale’s trade-off: branch-per-feature is a mindset shift. But schema migrations are easier than raw MySQL, and Vitess itself powers YouTube’s infrastructure.
The Real Comparison
| Metric | Firebase | Supabase | PlanetScale |
|---|---|---|---|
| Base Cost (1k DAU) | $800–$2,500 | $100–$250 | $39–$150 |
| Scaling Model | Pay-per-operation | Fixed tier | Fixed tier (billions of ops) |
| Database | Firestore (NoSQL) | PostgreSQL (SQL) | MySQL (SQL) |
| Setup Complexity | None (managed) | Low (managed Postgres) | Low (managed MySQL) |
| Query Flexibility | Limited (document-based) | Full (SQL + JSONB + advanced functions) | Full (SQL, window functions, CTEs) |
When Cost Breaks Down
A real scenario: SaaS app, 10k DAU, analytics job running hourly, real-time notifications enabled, 2GB stored data.
- Firebase: 10k users × 50 daily reads (page loads + background sync) = 500k reads/day = 15M/month. At $0.06 per 100k, that’s $90/month in reads alone. Add 100k writes/month ($0.108), storage ($0.18/GB), and network egress, and you’re looking at $400–$500/month minimum.
- Supabase: Buy the $200/month tier (includes 40GB). All queries, all reads, all writes — covered. $200/month.
- PlanetScale: 15M reads/month still fits the $39 starter. $39/month.
Firebase wins on ops complexity; Supabase wins on feature depth; PlanetScale wins on cost per operation.
How to Actually Choose
- If you have a mobile app or real-time sync is the core feature: Firebase has the real-time SDK baked in. Supabase can do it but requires more wiring.
- If you’re running complex queries, reporting, or multi-table joins: Postgres (Supabase) will save you engineering time and cost. Firebase requires workarounds.
- If you need the cheapest per-operation cost and don’t care about real-time: PlanetScale, hands down.
The meta-decision: don’t optimize for month 1. Optimize for month 12. A database choice at $39/month might become your biggest infrastructure bill at $3,000/month if you’ve chosen the wrong cost model.
If you’re building something more complex — multi-tenant SaaS, real-time dashboards, or APIs powering multiple clients — the database choice cascades into your entire backend architecture. That’s where working with an experienced engineering team pays off. Trove Deck Solution helps founders and SMBs navigate these kinds of infrastructure decisions during the discovery phase, so you’re not rewriting your database layer six months in. Reach out if you’re scoping a custom backend and want to validate your architecture before you commit.