Firebase

The Blaze plan is required more often than you expect

Firebase's free Spark plan is generous and permits commercial use, but there is a specific wall: deploying Cloud Functions requires the pay-as-you-go Blaze plan. On Spark you can develop and test functions locally with the emulator, but you cannot deploy them to production — and even once on Blaze, outbound network calls to non-Google services are a Blaze-only capability. Any function that calls a third-party API (a payment provider, an LLM, a webhook) means Blaze. Many projects discover this mid-build.

Practical implications

• Blaze is usage-based with no upper bound by default — set budget alerts. A misbehaving function or a traffic spike can run up a bill in a way Spark never could.
• Firestore is a NoSQL document store. Queries that are trivial in SQL (joins, aggregates) require denormalization or extra reads. Model your data for read patterns up front.
• Hosting with custom domains and SSL is free even on Spark — the static-hosting side is genuinely no-cost.

When to choose it

Firebase suits mobile-first apps and teams that want tight Google integration and realtime sync out of the box. If you want SQL and portability, Supabase is the alternative — see the comparison.