Cashtella
A multi-currency fintech wallet platform with an FX-conversion engine spanning NGN, USD, CAD, and USDC, backed by a double-entry ledger, KYC tiering, and a routed multi-provider payments layer.
- NestJS
- TypeORM
- PostgreSQL
- React
- Redis
- Bull
The challenge
Moving money across NGN, USD, CAD, and USDC means stitching together bank rails and crypto off-ramps that each model accounts, banks, and settlement differently, while still keeping one consistent ledger and one set of compliance limits for the user.
The approach
A NestJS backend centers on a provider-registry service that routes conversions, funding, and payouts to whichever third-party provider is configured per currency pair, with built-in failover across providers competing for the same route — including a genuine Yellow Card integration with an HMAC-signed client for live NGN/USDC rates, virtual NGN collection accounts, and NGN bank payouts. Money movement is recorded through a dedicated double-entry ledger module alongside wallet, transaction, and provider-account entities for atomicity and reconciliation. A KYC-tier service enforces daily deposit, transfer, and withdrawal limits per tier, with separate risk and sanctions-screening services. Inbound provider webhooks are verified, persisted for audit, and matched to users to credit wallets. Two front-end React apps consume the API: a customer-facing dashboard (wallets, payments, scheduled payments, invoices) and a separate staff admin dashboard (KYC review, audit log, OTC desk, revenue and exchange reporting, user management).
What’s live
- Multi-provider FX and payments routing with per-currency-pair failover
- Yellow Card integration: signed live rates, virtual NGN collection accounts, and NGN bank payouts
- Double-entry ledger module backing wallet balances
- KYC-tier system enforcing per-tier daily transaction limits
- Signed provider webhook ingestion with audit persistence and automatic wallet crediting
- Separate staff admin panel (KYC, audit log, OTC desk, revenue reporting) from the customer dashboard
