Lead Blockchain Full-Stack Engineer – High-Frequency Crypto Betting Infrastructure

Engagement Type: Full-time (40 hrs/week) / Long-term Retainer Budget: $80 – $150 / hr (commensurate with proven track record) The Context We are engineering a high-performance, non-custodial crypto-betting protocol that operates at the intersection of traditional sportsbook mechanics and DeFi primitives. The platform handles real-time odds streaming, automated market-making for liquidity pools, and on-chain settlement of multi-million dollar wagering volumes. We are not building a "casino dApp." We are building a low-latency financial trading engine where the asset class is sporting events. This requires an engineer who understands the fragility of blockchain RPC endpoints, the dangers of mempool congestion, and the mathematical rigor of provably fair systems. We have an existing MVP. We are now rebuilding the architecture for scale, security, and institutional-grade reliability. You will be the second engineering hire and will work directly with the CTO and the Head of Product. Core Technical Mandate You will own the end-to-end engineering lifecycle, specifically: 1. Backend & Microservices (Node.js) Design an event-sourced, message-driven architecture using NestJS with CQRS principles to handle 10,000+ concurrent betting events per second. Implement a dual-write pattern where critical state changes are written to PostgreSQL (via TypeORM/Prisma) and simultaneously published to Redis Streams for real-time WebSocket broadcasting. Build a resilient job scheduler (using BullMQ) to manage automated bet settlements, payouts, and expiry processes without blocking the main event loop. Architect a circuit-breaker pattern for external dependencies (blockchain RPCs, oracle data feeds) to prevent cascade failures during network congestion. 2. Blockchain & Smart Contract Interaction (EVM) Develop a robust transaction relayer service that manages a hot wallet for gas funding, implements nonce management across multiple chains, and handles transaction replacement (speed-up/cancel) during gas spikes. Build an event listener service that uses smart contract filters (logs) to detect deposits, withdrawals, and bet placements. This service must implement checkpointing and re-org resilience (handling chain reorganizations up to 15 blocks deep). Write and deploy Solidity smart contracts (Hardhat/Foundry) for: Betting pools with merkle-distribution for reward claims. Escrow logic with time-locked withdrawals. ERC-20 wrapper for stablecoin settlements. Integrate with The Graph Protocol for subgraph indexing to offload query load from the RPC nodes. 3. Frontend (React.js) Architect a headless UI system using React 18 with concurrent features and Suspense for data fetching. Implement a real-time data layer using TanStack Query (React Query) for server-state management, combined with a custom WebSocket hook that handles binary protocol (MessagePack or Protobuf) for bandwidth efficiency. Optimize the rendering of dynamic odds boards and in-play animations to maintain 60 FPS using useMemo, useCallback, and virtualization (react-window). Manage complex form state (multi-leg parlays, system bets) using React Hook Form with Zod validation. 4. Security & Operational Integrity Implement hardened key management using HSMs or cloud KMS (AWS KMS / GCP Cloud KMS) for transaction signing—no private keys in environment variables. Build a comprehensive audit logging system tracking all administrative actions, user bet placements, and system-level state changes (immutable log). Design a rate-limiting and anti-fraud layer that detects arbitrage patterns and suspicious account behavior using sliding window counters in Redis. Non-Negotiable Requirements 7+ years of professional software engineering experience, with 4+ years in Node.js and 3+ years specifically working with EVM-compatible blockchains in a production environment (not hackathons or tutorials). Proven experience building a system that handled real-money transactions (fintech, trading, gaming, or DeFi). We will ask for specific throughput metrics (TPS, latency percentiles). Deep understanding of the Ethereum mempool: priority fees, blob transactions (EIP-4844), and the risks of front-running and sandwich attacks. Production experience with at least one of: Redis Streams, Apache Kafka, or RabbitMQ for event-driven architectures. Expert-level proficiency in TypeScript —you use unknown over any, you leverage discriminated unions, and you write strict, inferable types. Database expertise: You can explain the difference between read-committed and repeatable-read isolation levels and have optimized complex SQL queries with EXPLAIN ANALYZE. DevSecOps awareness: You have used Docker, Kubernetes (EKS/GKE), and have set up observability stacks (Prometheus/Grafana/OpenTelemetry) to monitor both application and blockchain node health. Interview Process (Transparent) We respect your time. The process is rigorous but efficient: Stage 1: reviewing CV. Stage 2: taking assessment. Stage 3: technical meeting with CTO. Stage 4: final meeting and onboarding How to Apply: To prove you have read this post, please start your proposal with the word "CryptoPro". In your cover letter, please provide: A specific example of a Node.js application you built that handled high concurrency. Your experience with transaction monitoring (detecting incoming payments). Links to your GitHub/Portfolio (smart contract or full-stack projects). Note: We are only considering senior-level candidates with active blockchain experience. Please do not apply if you are an agency or have only done basic token swaps.