We migrated 3 SaaS apps off Firebase. Here is when to stay, when to leave, and what to switch to.

By David Friedman , Founder of AppBrewers

Firebase is the default backend for MVPs. But at 10,000+ users, costs spike and limitations appear. We migrated 3 SaaS apps off Firebase in 2025. Two went to Supabase. One went custom. Here is how to decide.

When Firebase Is Perfect

Stage Users Firebase Cost Why It Works

MVP 0-1,000 0-50 Euro/month Free tier covers everything.

Growth 1,000-10,000 50-300 Euro/month Still cheap, still scalable.

Scale 10,000-50,000 300-1,500 Euro/month Costs rise but manageable.

Enterprise 50,000+ 1,500-5,000 Euro/month Time to evaluate alternatives.

Firebase Limitations at Scale

Limit Impact Workaround

Firestore query limitations Complex joins are hard Denormalize data

Cloud Functions cold starts 2-5 second latency Keep functions warm

Vendor lock-in Hard to migrate Abstract data layer early

Real-time costs 100K+ concurrent connections gets expensive Use polling for…