Onsite Technical Lead (Fullstack) – Fintech 🚀

At ArrowFin, we support the construction and optimization of high-performance technology solutions that power our clients' trading activities directly on the Chicago Mercantile Exchange (CME). We develop our own software—no outsourcing or third-party client work—backed by an engineering team focused on real-time systems and distributed architecture. RoleWe are hiring an Onsite Senior Full Stack Engineer (Technical Lead) for our office in El Poblado, Medellin. The role has a dual purpose: ship production code for our real-time streaming trading products, and serve as the onsite technical anchor and mentor for our local engineering team. Key Responsibilitieso   Full Stack Development: Design and build resilient backend microservices and REST APIs, alongside complex, high-performance frontend interfaces. o   Leadership & Mentorship: Lead code reviews, mentor local mid-level engineers, and translate product requirements into clear, unambiguous technical specifications. o   Real-Time Systems & Security: Maintain WebSocket data flows, optimize PostgreSQL queries, and ensure strict multi-tenant data isolation and security standards. o   Local Escalation: Act as the primary technical responder during Colombia business hours for staging and production incidents. Required Stack & QualificationsHard Requirementso   Location & Language: B2 or higher English proficiency and based in surrounding areas of Medellín or open to relocate (onside role). o   Experience: 7+ years in professional full stack web development, including at least 2 years in a Senior or Tech Lead role. o   Backend: Deep expertise in Node.js / TypeScript (NestJS) and clean/hexagonal architecture. Willingness to work in a polyglot backend environment. o   Frontend: Strong mastery of React + TypeScript, state management, and high-frequency UI updating components. o   Database & Real-Time: Solid PostgreSQL experience (query optimization, indexing, and migrations) alongside WebSockets or event-driven patterns. Nice to Haveo   Background in Fintech, trading, brokerage, or other low-latency regulated environments. o   Familiarity or interest in Rust. o   Exposure to DevOps and Observability tooling (Docker, Prometheus, Grafana).