How we shipped a FinTech super-app to 1.4M installs at 99.97% crash-free
Where they were stuck.
The company had spent 14 months building a React Native app that couldn't scale past 80K users without crashes. Their CTO had inherited it from a previous team and wanted out. They were 6 weeks from a regulator-driven launch deadline with no working product. The original agency was non-responsive. We were brought in for a 'rescue audit' that turned into a full rebuild.
What we did, step by step.
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01
Native iOS (Swift + SwiftUI) and native Android (Kotlin + Compose) rebuild from scratch — same backend, same APIs.
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02
Modular architecture: 14 feature modules so the 8-person engineering team could ship in parallel without merge conflicts.
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03
KYC integration with 4 different providers (per-region compliance), each behind a unified abstraction so the app code didn't care which one was active.
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04
Real-time portfolio data via WebSocket connection with retry logic, queueing, and reconciliation on reconnect.
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05
Crash reporting wired to Firebase Crashlytics + Sentry with custom severity classification — critical bugs paged the on-call engineer immediately.
What changed.
The app shipped 11 days before the regulator deadline. By month 6 it had crossed 1M installs and was processing $40M in transactions monthly. Crash-free rate stayed above 99.95% even at peak load. The internal engineering team adopted our patterns for the rebuild and we transitioned out as advisors on a small retainer.
The app they shipped is fast, beautiful and rock-solid. 99.97% crash-free at 1M+ installs — our internal engineering team is genuinely impressed.
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