Card Pay
Secure peer-to-peer mobile payment solution.
What we built
and why.
CardPay is a secure peer-to-peer mobile payment solution built with Flutter for iOS and Android. We engineered a Clean Architecture codebase with bank-grade transaction flows, tap-to-pay support, multi-card wallet management, and real-time spending analytics, all wrapped in an interface that feels closer to Apple Pay than a traditional banking app.
The problem
to solve.
Context
FinTech · Consumer Payments : The client needed a modern P2P payment product that could rival the best consumer fintech apps on launch day. Compliance, speed, and delight were non-negotiable.
Core Problem
Traditional banking apps ship slow, feel dated, and silo each product. The market needed one wallet that handled cards, transactions, insights, and tap-to-pay, without the trade-off between security and UX.
How we
built it.
A 12-week build from zero to production. Two-week design sprint, eight-week development in parallel, two-week QA and compliance pass. Clean Architecture to keep the business logic testable and reusable across platforms.
Discovery & Compliance
Mapped the full transaction lifecycle, KYC/AML requirements, and payment-rail integrations before writing any UI.
Design System
A modular design system covering 60+ screens with a single source of truth in Figma, exported into a custom Flutter theme.
Build Sprints
Parallel feature teams shipped wallet, tap-to-pay, transaction history, and insights modules on a weekly demo cadence.
Launch & Harden
Instrumented observability, ran penetration tests, and shipped to both app stores with a staged rollout.
What got
shipped.
A Flutter codebase split into feature modules on top of a Clean Architecture core. Secure storage for tokens, encrypted local cache for offline transactions, and a BLoC-based state layer that makes every screen unit-testable without mocking the backend.
Key Innovations
- Biometric-first login with fallback PIN + device binding
- Transaction animations synced to haptics for confirmation feedback
- Category-aware spending insights powered by on-device ML
- Offline-first transaction queue with conflict resolution on reconnect
Obstacles Overcome
- Integrating two separate payment rails (cards + peer transfers) under one UX without confusing users
- Meeting PCI-DSS guidelines while keeping the onboarding under 90 seconds
- Apple and Google security review feedback required two rounds of hardening
What it
does.
5 core capabilities that define the product. Each engineered with a senior team, tested against real usage, and shipped to production.
Digital Card Wallet
Sleek interface for managing multiple credit/debit cards.
Tap-to-Pay
Secure contactless transactions integrated directly.
Transaction History
Categorized logs with immediate spending alerts.
Spending Insights
Visual analytics to track and understand financial habits.
Secure Management
Unified dashboard with high-level encryption protocols.
The product,
end to end.
11screens from the shipped build. Every flow, every state. These aren’t renders, they’re production.
The impact,
measured.
Shipped end-to-end in 12 weeks across both platforms with a security posture that passed an independent fintech audit on the first pass, enabling the client to launch to market on-schedule and onboard users without regulatory friction.
Built with.
CardPay proved that a small senior team can ship a regulated fintech product in a quarter, with the craft, the compliance, and the performance budgets you'd expect from a team 5× the size.
Got a project that
needs this kind of build?
Tell us the problem. We’ll tell you if it’s a 2-week sprint or a 2-month platform, honestly, in the first call.
