About the role
We're looking for a mid-level to senior Flutter engineer who understands DeFi — not just how to build a beautiful mobile app, but how DeFi products (lending, staking, swaps, savings, and self-custody wallets) actually work on-chain. You'll build consumer-facing DeFi products end to end, translating complex on-chain flows into interfaces that are clear, trustworthy, and delightful. You'll collaborate closely with backend, product, and design to ship money-movement features that are secure and reliable.
About KAST:
KAST is redefining stablecoin banking for global citizens, crypto professionals, Web3-native businesses, and high-inflation markets hungry for USD-backed banking. Backed by top-tier global investors and led by the ex-APAC CEO of Circle, the leadership team spans Circle, Airwallex, Revolut, Wise, Grab, Zoom, AWS, and leading OTC desks. KAST has scaled from zero to nearly a million users at high speed.
What You'll Be Doing:
Build and own consumer-facing DeFi features in the KAST mobile app, end to end
Translate DeFi concepts (lending, swap, borrowing) into clear, trustworthy mobile UX
Integrate with backend services and handle secure, multi-step money-movement and transaction authorization flows
Handle wallet, signing, and transaction states — pending, submitted, confirmed, failed — with robust error handling and user feedback
Contribute to a clean, well-tested mobile architecture and shared component patterns
Write testable, maintainable code and participate in code review and release quality
Collaborate with product and design to shape requirements into shipped features
What we're looking for
What You'll Bring:
2+ years of production mobile development with Flutter, or 3+ years with ownership of shipped consumer apps
Hands-on DeFi experience required — built, integrated, or worked closely with on-chain protocols (lending/borrowing, staking, swaps, or wallets) and understand concepts like collateral, LTV, health factor, and gas/network fees
Strong command of Flutter fundamentals: state management, navigation, clean architecture, and dependency injection
Experience consuming REST APIs, handling auth tokens, and managing complex asynchronous and multi-step transaction flows
Solid understanding of mobile security best practices (secure storage, sensitive data handling, MFA flows)
Comfortable with Git-based workflows, code review, and shipping to the App Store / Play Store
Nice to Have:
Experience integrating with DeFi lending, staking, or swap protocols on any major chain
Familiarity with embedded/MPC wallet providers or self-custody / key import-export flows
Experience in fintech, neobanking, or regulated financial products
Exposure to mobile analytics/observability and CI/CD
Contributions to shared Flutter packages or a modular multi-app codebase