YeneCard: Production Fintech Card and Wallet Platform

How I helped a fintech client turn YeneCard into a production-ready card and wallet platform

The challenge The client needed more than a card interface. They needed a dependable financial system that could support customer onboarding, KYC, wallets, virtual USD cards, funding, transfers, transaction history, provider integrations, operations, and support without losing control of money movement or sensitive data.

My role I worked as a hands-on technical partner across product decisions, architecture, backend, mobile, web, security, testing, infrastructure, migration, and production operations. I helped translate business workflows into clear system boundaries and delivery milestones, then implemented the critical paths.

The solution • Flutter mobile application and responsive customer web experience • Java 17/21 and Spring Boot REST APIs • PostgreSQL ledger and reliable money movement in minor currency units • KYC documents, selfies, review states, and wallet or card activation gates • Authentication, MFA, PIN protection, RBAC, step-up security, and audit logs • Card-provider abstraction for issuing, funding, freezing, and transaction events • Signed webhooks, duplicate protection, idempotency, reversals, and reconciliation • Admin operations for users, cards, wallets, KYC, providers, pricing, and support • JUnit, Testcontainers, Flutter integration tests, and Playwright coverage • Docker, CI/CD, monitoring, migration tooling, and production documentation

Key technical decisions The platform keeps provider-specific behavior behind adapters, separates wallet and card accounting from external provider state, and treats every money-moving operation as an auditable workflow. Reconciliation tools detect drift instead of trusting synchronized copies blindly. Sensitive data is encrypted or excluded from storage, and privileged actions require explicit authorization and step-up controls.

Outcome The resulting platform supports more than 20,000 customers and 30,000 issued USD cards. More importantly, the client received a system that can be operated, reviewed, extended, and handed over without depending on hidden business logic or fragile manual fixes.