mobile·2026·Solo Mobile Engineer
Privvy Ledger
Privvy Ledger is a privacy-first expense tracker that keeps financial data where it belongs — on the device. No account, no cloud, no ads. Receipts are scanned by an on-device pipeline (MLKit OCR plus a quantized LLM via ExecuTorch), backups are AES-256-GCM encrypted files the user owns, and the entire 'Vault' design system — OLED midnight theme, monospace figures, haptics — is original IP, built to replace the template UI it launched with. Shipped solo on a public 2–3-week release cadence, shaped release-by-release by a live tester group.
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Stack
- React Native
- Expo
- TypeScript
- SQLite
- twrnc
- MLKit + ExecuTorch (on-device AI)
Highlights
- Receipt scanning that never leaves the phone — MLKit OCR feeding a quantized Qwen LLM via ExecuTorch; reads images and PDFs from six Nigerian bank/fintech formats, fully offline after a one-time model download
- Extraction engine hardened by a regression harness of real OCR output — every bank format that ever parsed wrong becomes a permanent fixture, so fixes can't regress
- Security in layers: PIN + biometric unlock, brute-force cooldown with auto-wipe, auto-lock on background, and a native app-switcher privacy cover via a custom Expo config plugin injecting Kotlin
- AES-256-GCM encrypted backup and restore (PBKDF2-derived keys) — export anywhere, restore on any device, no server involved
- Original 'Vault' design system: OLED midnight + warm Paper themes, JetBrains Mono for every financial figure, haptic feedback throughout — template UI replaced with owned IP in a single release
- Budgets with 80%/100% threshold push alerts, an in-app notification center, demo mode for first-run exploration, and CSV + branded-PDF statement exports