Senior Backend Developer (Barcelona)

Who you are

• Advanced Python — non-negotiable. Clean, tested, reusable code. Not just scripts that happen to work
• API design and implementation. Designing and maintaining REST APIs with clear contracts, versioning, and proper error handling
• Software engineering discipline. Testing, code review, Git, and the habits of someone who builds things that others can maintain
• Ability to work in a mixed-language codebase. The existing platform is Python/C#. You need to be comfortable reading it and understanding the integration points
• C#: You will also work with the existing platform, you need to write quality, clean, testable code in C#
• Familiarity with AWS services (Lambda, API Gateway, S3) or equivalent cloud infrastructure
• Experience with API specification tooling (OpenAPI/Swagger, Pydantic, etc.)
• Exposure to Python packaging, dependency management, and CI pipelines
• Familiarity with constraint-solving ...