A multi-currency wallet that holds, converts and moves money across borders in real time, built mobile-first on React Native, settled through Stripe, and backed by a ledger that never loses a cent.
In fintech the hard part isn't moving money, it's proving you moved it correctly. Every balance change is written as a double-entry pair inside a single PostgreSQL transaction, so a debit can never exist without its matching credit, even mid-crash.
Idempotency keys on every Stripe call mean a retried request can't double-charge a user. A nightly reconciliation job replays Stripe's settlement report against our ledger and halts on any penny of drift.
Users hold balances in several currencies at once. When they convert, we lock a marked-up mid-market rate for 30 seconds so the number they tap is the number they pay, no slippage between quote and settle.
FX legs are stored as their own ledger entries, keeping conversion spread fully auditable and every wallet balance independently provable down to the minor unit.
| Component | Technology | Why |
|---|---|---|
| Mobile client | React Native | One codebase, native feel, faster iteration on iOS + Android |
| API & business logic | Node.js | Async I/O suits high-volume, I/O-bound payment flows |
| Ledger & data | PostgreSQL | ACID transactions guarantee double-entry integrity |
| Payments & FX | Stripe | PCI-compliant rails, 3DS, and built-in idempotency |
| Infra & delivery | AWS | Auto-scaling, SNS push, and audited compliance posture |
Hold, view and spend balances across several currencies from one account.
30-second rate guarantee so the quoted amount is exactly what settles.
Stripe-powered funding with 3D Secure and instant balance updates.
Atomic debit/credit writes make every balance provable and audit-ready.
Nightly Stripe-vs-ledger replay catches drift before it ever reaches a user.
AWS SNS push alerts on every send, receive and conversion event.
“In a wallet, every cent has to be provable, so we made the ledger, not the UI, the source of truth.”
The result is a wallet that scaled to 35K+ downloads and 120K+ transactions a month while keeping a 4.7-star rating, and, just as importantly, never breaking reconciliation. By treating the PostgreSQL ledger as the source of truth, locking FX rates before settlement, and leaning on Stripe and AWS for compliant rails, the app delivers the speed users feel and the integrity auditors demand from the same codebase.