Senior Full-Stack TypeScript Engineer — Web3 / FinTech / Trading

Senior Full-Stack TypeScript Engineer needed for a product at the intersection of Web3, fintech, and trading. Must handle both frontend and backend, make technical decisions independently, and deliver features end-to-end. Tech stack: TypeScript, React, Next.js, PostgreSQL, WebSockets, blockchain integrations.

Develop and evolve a product using TypeScript / React / Next.js. Work on both frontend and backend. Build interfaces with large amounts of real-time data: prices, positions, orders, and other constantly updating data. Work with WebSockets: correctly handle connection drops and reconnections. Design data structures and work with PostgreSQL. Integrate blockchain, wallets, and external services. Work with financial logic where correctness of operations and data consistency are critical. Develop a full-fledged mobile web interface. Integrate and maintain external APIs and services. Use Claude Code as part of daily development workflow.

Candidates must reside outside Russia and Southeast Asia. 5+ years of commercial development. You continue to write code yourself, not only manage a team. Confident TypeScript on both frontend and backend. Strong experience with React and Next.js: App Router, Server Components, SSR. Experience with PostgreSQL: independent design of tables, relations, and writing queries. Experience launching at least several products or large parts of a product to real users and end-to-end responsibility. Experience in fintech, crypto, trading, payments, wallets, or other systems with real financial operations. Understanding of financial systems: protection against duplicate operations, correct error handling, and inability to simply roll back part of blockchain transactions. Experience with WebSockets / streaming / real-time data. Experience developing applications with a large flow of constantly updating data and understanding of interface performance. Understanding of state management and client-side data caching: React Query or similar. Experience with blockchain integrations: wallets, signing operations, reading on-chain data. Experience with viem or ethers. Experience creating interfaces that are actually convenient to use from a phone: touch interface, mobile Safari, keyboard, safe areas, and other mobile device features. Ability to independently work with a large number of external integrations and figure things out even with incomplete or poor documentation. Strong engineering background: you can independently write, read, analyze, and debug code. In your current work, you have already switched to Claude Code and use it as your main working tool. We need a developer who can do everything independently if necessary, but now actively and daily works through Claude Code. Nice to have: Experience developing prediction markets, especially Polymarket, Kalshi, or similar products. Experience with trading systems and order book. Understanding of market and limit orders, partial fills, slippage. Experience with embedded wallets: Magic, Privy, Web3Auth, Para. Experience with relayers, meta-transactions, gas sponsorship. Knowledge of ERC-4337 / Account Abstraction. Experience reconciling own database data with blockchain. Experience with cross-chain bridges. Experience with Polygon. Experience with Supabase.