Senior Backend Developer

Senior Backend Developer, Serbia

We’re looking for a Senior Backend Developer who challenges assumptions, builds with intention, and thrives in a fast-moving, AI-driven environment.
At 3ap, engineers own their work end-to-end. Our teams run on separate projects but solve hard problems together, share what they learn, and call out bad assumptions, including their own.

 What we need:

• 5+ years with Java/Spring
• Solid REST API design and integration experience
• Hands-on with Docker, Kubernetes, Jenkins, and OpenShift
• Rigorous about testing, especially where AI outputs are involved
• Comfortable with API tools like Postman or Insomnia
• You think about the full product, not just your layer. A bad integration can sink a good solution
• You don’t stop at “it works.” You look for the flaw in the logic before someone else finds it in production
• You pick up new tools fast. The AI landscape shifts week to week, and waiting to learn something familiar isn’t an option
• You treat AI output as a draft, not a deliverable. You build guardrails, test rigorously, and verify manually
• You’ve used GitHub Copilot, Claude, or similar in your actual workflow
• You communicate clearly and don’t need much hand-holding to unblock yourself
• University degree in CS or equivalent
• Fluent English

 Useful, but not required:

• WebFlux / reactive programming
• Node.js, PostgreSQL, MongoDB, React, Angular, or Vue
• CI/CD and DevOps hands-on experience
• Prompt engineering or multi-step AI workflows
• Comfort and openness to working with Python. Many modern AI tools and frameworks are built with Python at their core, so a willingness to learn and use it is important.
• Background in insurance or finance
• Any German

 What you get:

• A team of 50+ professionals in a people-first culture, flat structure, and no bureaucracy
• Work that uses current technology, including AI in production
• Flexible hours, hybrid work
• 25 vacation days + 2 extra 3ap holidays
• Private pension, private health insurance, 24/7 accident insurance
• Maternity and paternity leave support
• Team events and an employee referral program