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Case 06 · Crypto · Cards

From stablecoins to a card paymentin one app.

On- and off-ramps, custody and a card program for a digital-asset company — so customers move between stablecoins and traditional money as easily as using a bank card.

Client name withheld under NDA
Industry
Crypto & digital assets
Region
Global
Engagement
Product Team · Discovery to support
Services
Fintech & Digital Assets · Product Engineering · Product Design

The challenge

A digital-asset company wanted its customers to buy and sell USDT and USDC, withdraw to bank accounts and spend with a card — all in one app. That meant connecting custody, banking and card-issuing partners, keeping on-chain and off-chain balances in sync, and meeting strict compliance requirements in every flow.

What we built

  1. On- and off-ramp flows: bank transfer or card in, stablecoins out — and back again — across several networks, including TRON and Ethereum.
  2. Integration with a custody provider, with on-chain monitoring of deposits and withdrawals.
  3. A card program with an issuing partner: virtual and physical cards funded from a stablecoin balance, with real-time authorization.
  4. KYC onboarding, wallet screening, Travel Rule data exchange and transaction monitoring.
  5. Mobile and web apps for customers, and a back office for support, compliance and treasury.

How we did it

Before design started, we mapped every money and token flow with the compliance team. A ledger reconciles on-chain and off-chain balances, and the card authorization path was engineered separately for low latency and high availability.

  • Compliance checks designed into each flow, not added afterward
  • Staged launch by region, with limits raised as monitoring confirmed stability
  • Key management through managed HSM and KMS services

The outcome

  • Customers move between crypto and traditional money in one app
  • On-chain and off-chain balances reconciled automatically
  • Compliance built into every flow from day one
  • An architecture ready for new networks, currencies and regions

Stack

  • TypeScript
  • Node.js
  • React Native
  • Go
  • PostgreSQL
  • Kafka
  • TRON
  • Ethereum
  • USDT
  • USDC
  • AWS KMS

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