Senior Software Engineer (Frontend Focus)

About the company: Kiefer Tech, the technology arm of Kiefer, leverages over 12 years of engineering heritage from the Green Energy sector to deliver cutting-edge AI, robotics, and enterprise solutions across Greece and the EU. We build sovereign AI infrastructure that keeps data within EU borders, respect privacy, and delivers tangible business impact. Guided by our core values: innovation, quality, and long-term client partnerships, we create enterprise-grade AI infrastructure, the first true Greek Large Language Models, and intelligent automation solutions that empower organizations to thrive. Our strategic collaboration with NVIDIA combines sustainable infrastructure expertise with world-class AI technology, creating an ecosystem that fosters innovation, strengthens Greece’s technological sovereignty, and generates real impact across industries. Join us and help build the AI-powered world of tomorrow. About the role: We are looking for a Senior Software Engineer with strong frontend expertise to take ownership of product surfaces within Sophea Nous, our enterprise AI search and assistant platform. Sophea Nous connects to the places where a company’s knowledge already lives and allows users to search, receive answers with verified citations, and work with AI assistants and agents. The platform is multi-tenant, self-hosted, and already used by enterprise customers. You will own features end to end, including the interface, supporting backend, automated tests, release, and production behaviour. You will work closely with a product manager and UI/UX designer from the early stages of product development, helping decide what should be built and how it should work. This is a large, live codebase that needs to evolve incrementally. The role offers significant technical autonomy and ownership across web, mobile, and desktop. It is not a maintenance role. Our stack includes TypeScript, React, and Next.js for web, React Native with Expo for mobile, and Electron for desktop. The backend is built with Python, FastAPI, and Celery, using PostgreSQL and Redis. It also includes a retrieval service and an LLM gateway connected to our own GPU infrastructure. Everything runs on Kubernetes. What You Will Do Own Sophea Nous product surfaces end to end across web, mobile, and desktop. Guide client architecture and keep web and native applications aligned around shared patterns. Improve inherited parts of the codebase incrementally, without unnecessary rewrites. Build interfaces for streaming AI answers, citations, long chat histories, document viewers, and reliable reconnection. Work with UI/UX from the early design stage and contribute to the Python backend when a feature requires the full product flow. Build automated test coverage, apply security principles from the design stage, and use AI and browser agents to support development and validation. What you will need: 6+ years of professional software engineering experience, with frontend development as your core expertise. Strong experience with TypeScript, React, React Native, and Next.js, including applications shipped and maintained in production across web, Android, and iOS. Strong understanding of server and client state management, with experience improving the architecture of a large existing codebase incrementally. Good understanding of UX principles and enough Python knowledge to extend a FastAPI service and work with PostgreSQL when needed. Hands-on experience with test automation and AI agent workflows, including the ability to critically review their output and limitations. High autonomy, strong communication skills, and the ability to collaborate effectively with engineering, product, and design teams. Nice to have: Experience with LLM products, chat interfaces, streaming, citations, RAG, search, or vector databases. Experience with shared design systems, Expo, EAS, Electron, or mobile release pipelines. Experience with frontend performance, real-time delivery, end-to-end testing, accessibility, or internationalisation. What is there for you: Fully remote within the EU, or hybrid from Athens — no relocation expected. 28 weekdays of paid annual leave (in Greece). Compensation benchmarked against the Greek and EU market, private health insurance or the remote-EU equivalent. Architecture ownership across three clients from day one, with specialists to lean on rather than wait for. Daily work with LLMs, agent workflows and AI infrastructure. Budget for conferences, courses and certifications.