Senior Backend Engineer (Node.js / NestJS) – Greenfield Product

Castle Tech GmbH is looking for a Senior Backend Engineer to join on a freelance basis for 9–12 months. The role involves shaping the product's architecture, backend services, and technical direction using Node.js and NestJS. The ideal candidate will have 5+ years of backend engineering experience, strong experience with TypeScript, Node.js, and NestJS, and a strong understanding of software design principles and maintainable systems.

Requirements

• 5+ years of backend engineering experience
• Strong experience with TypeScript, Node.js, and NestJS
• Experience designing scalable backend architectures
• Strong understanding of software design principles and maintainable systems
• Experience with relational databases (PostgreSQL or similar)
• Experience working with Git, CI/CD pipelines, and Docker
• Experience mentoring or supporting other engineers
• Experience working in agile teams (Scrum or Kanban)
• Strong communication skills in English (written and verbal)

Benefits

• Flexible work arrangement
• Real technical ownership
• Modern engineering environment
• Collaborative team
• International exposure