Frontend Developer (Flutter; DeFi)

KAST; New York (NY); On-site; USD 120,000 - 180,000; Full time

Job summary

KAST is seeking a mid-level to senior Flutter engineer who understands DeFi to build end-to-end consumer DeFi products. You will translate on-chain flows into clear mobile UX, collaborate with backend, product, and design to ship secure money-movement features, and own wallet and transaction states.

Ideal candidates have 2+ years of Flutter experience (or 3+ years with shipped apps) and hands-on DeFi experience across lending, staking, swaps, or wallets. Remote work from the US is supported.

Qualifications

• 2+ years of production mobile development with Flutter or 3+ years with shipped apps.
• Hands-on DeFi experience with on-chain protocols (lending/borrowing, staking, swaps, wallets).
• Strong Flutter fundamentals: state management, navigation, clean architecture, DI.
• Experience consuming REST APIs and managing complex asynchronous and multi-step transaction flows.
• Mobile security best practices and secure storage; MFA flows.
• Git-based workflows, code review, and app store deployment.

Responsibilities

• Build and own consumer-facing DeFi features in the KAST mobile app, end to end.
• Translate DeFi concepts into clear, trustworthy mobile UX.
• Integrate with backend services and handle multi-step money-movement transactions.
• Handle wallet, signing, and transaction states with robust error handling and user feedback.
• Contribute to a clean, well-tested mobile architecture and components.
• Write testable code and participate in code reviews and releases.
• Collaborate with product and design to shape requirements into shipped features.

Skills

Flutter

Mobile development

DeFi experience

REST APIs

Security best practices

Git workflows

Tools

Flutter SDK

Dart

CI/CD

Job description

Description

Department: Engineering

Location: New York

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.

Location: remote from the US.

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 You'll Bring

• 2+ years of production mobile development with Flutter, or 3+ years with ownership of shipped consumer apps.
• Hands-on DeFi experience is required - you have 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.