Senior Node.js / Crypto Market Data Engineer

I am seeking a senior developer or small agency to build and initially operate a secure, web-based cryptocurrency spatial-arbitrage paper-trading platform. This is paper trading only: no live order execution and no withdrawal permissions. The system requires Node.js/TypeScript, PostgreSQL, React, Docker, WebSockets, CCXT-compatible exchange integrations, real-time price and Level 2 order-book capture, a deterministic rules engine, persistent data storage, deterministic replay, configurable slippage and fee modelling, balance management, kill switches, audit logs, authentication, encrypted API-key storage, backups, monitoring, and cloud deployment. The platform must capture real market data, support reproducible replay, and run a 60-day paper-trading validation period. AI must not be in the execution decision path. Required experience: • Node.js / TypeScript, PostgreSQL, Docker and Linux deployment • WebSocket market-data systems and exchange APIs • CCXT or comparable multi-exchange integration experience • Automated trading safeguards, persisted kill-switch state, security and API-secret management • Clear English documentation and willingness to explain technical decisions to a non-technical founder Please provide: • Two relevant examples • Your proposed architecture and cloud recommendation • A paid two-week discovery proposal • Fixed-price or milestone-based quotation • Explicit assumptions and exclusions • Confirmation that all IP, source code, cloud accounts, domains, credentials and documentation remain under client ownership Developers who propose using generic trading-bot templates, unverified “AI agents,” or live trading before a 60-day paper-trading validation period will not be considered. This is the first part of a much larger project and may become a full time role.