Back-End Developer

Employment: Full-time Salary: $2,800–3,500 net (depending on interview results and experience) Probation Period: 1 month (salary during probation depends on the candidate's actual range) About the Project We're building a slots game engine on a modern Node.js stack: round state machine, provably-fair mechanics, and reliable transactional logic for a multi-currency financial platform. The challenges revolve around deterministic computation, money-calculation precision, and balance consistency under load. Our Tech Stack Node.js · TypeScript · Fastify · PostgreSQL · WebSocket/Socket. IO · Firebase Auth · Provably Fair (HMAC-SHA256) · BigInt · Docker Responsibilities Design the game engine using Node.js, TypeScript, and Fastify: round state machine, outcome taxonomy, autoplay, bet cancellation. Implement Provably Fair (HMAC-SHA256) with server-side generation and verification, plus BigInt arithmetic for money calculations. Develop the wallet and transactions: multi-currency support, deposits/withdrawals, idempotency, balance consistency. Build platform logic: KYC, VIP levels, affiliate program, leaderboards, notifications. Integrate an external betting API (Axios: auto-refresh, circuit breaker), real-time layer (WebSocket/Socket. IO), and authorization via Firebase. Work with PostgreSQL and containerization (Docker/Compose); cover critical logic with tests. Requirements (must-have) 3+ years of back-end development experience with Node.js and TypeScript (Fastify/Express preferred). Experience designing transactional logic (balances, payments, idempotency) and working with PostgreSQL. Understanding of deterministic computation and money-calculation precision (BigInt / decimal), state machines. Experience integrating external APIs and real-time communication. Middle+: autonomy, testing, code review, attention to security. Experience in iGaming/Casino, provably-fair/cryptography (HMAC-SHA256), RNG mechanics. Nice to Have Firebase Auth (2FA TOTP), experience with KYC/AML, VIP/affiliate systems. Familiarity with regulated betting and high-load financial systems.