Senior Full Stack Developer (.NET / React / AI - remote B2B

We are looking for an experienced Full Stack Developer (. NET / React) who has real, hands-on experience building AI-powered solutions or features. We are specifically looking for developers who have gone beyond simply using GitHub Copilot or other AI coding assistants. You should have actually designed, developed, integrated, or deployed AI functionality within a commercial application or product. Location: Remote – PolandLanguage: Polish and EnglishStart: September 2026Contract: 12 monthsInterview process: 1 interview onlyKey ResponsibilitiesDesign and develop full-stack applications using C# / . NET and React. Build scalable backend services, REST APIs and integrations. Design and implement AI-powered features as part of real applications or products. Integrate applications with LLMs and AI services such as Azure OpenAI, OpenAI or similar platforms. Work with technologies and concepts such as RAG, AI Agents, prompt orchestration, vector search, embeddings or intelligent automation, depending on the use case. Take AI solutions from idea/prototype through integration and production implementation. Work closely with architects, product owners and engineering teams. Required Skills5+ years of commercial C# / . NET experience. Strong hands-on experience with React and TypeScript. Experience developing REST APIs, backend services and/or microservices. Azure or another major cloud platform. Git, CI/CD and modern software engineering practices. Strong Polish and English communication skills. AI Experience – ImportantWe need someone with practical AI development experience, not only exposure to AI tools. You should have built or contributed to at least one solution involving areas such as: LLM integration within a commercial application. RAG (Retrieval-Augmented Generation) solutions. AI Agents / agentic workflows. Integration with Azure OpenAI, OpenAI APIs or similar AI platforms. Vector databases, embeddings or semantic search. AI-powered document processing, classification, extraction or summarisation. Intelligent workflow/process automation using AI. Custom AI assistants or conversational applications. Other production AI/ML functionality integrated into software products. We are interested in developers who can clearly explain what AI solution they built, what problem it solved, which technologies they used, and what their personal contribution was.