Senior Fullstack AI Engineer (f/m/d)

Job description For years, StackFuel has been one of Germany’s leading providers of data and AI training. Since early 2026, we have been part of Multiverse, Europe’s only EdTech unicorn and the continent’s largest AI upskilling platform. Together, we are pursuing a clear goal: to make 100,000 employees in Germany AI-ready and close the country’s data and AI skills gap. To make this happen, we are building a next-generation adaptive learning platform from Berlin, AI-first from the ground up. Alongside this, we develop software tools and automations that integrate into our customers’ B2B platforms. As a Senior Fullstack AI Engineer (f/m/d), you’ll play a key role in shaping this platform and these software tools, from the database to the frontend. Your work directly reaches thousands of learners and contributes to the transformation of mid-sized and large German companies. Your responsibilities • Develop our adaptive, AI-first learning platform and software-based AI solutions end-to-end, independently making key technical architecture decisions • Implement new features and requirements in our existing learning framework, balancing new development with ongoing improvements • Build AI features into the platform, such as LLM-powered learning support, adaptive learning paths, or automated content generation, and ensure they run reliably, measurably, and cost-efficiently • Build internal tools and AI automations for Learning Coaches, Client Operations, and Sales to help these teams work more efficiently • Work closely with the entire engineering team, our Content Engineering team, and the Portfolio Leads What you bring • 5+ years of experience in full-stack development, several of them with senior responsibility (architecture, technical decisions, mentoring) • You work AI-first and naturally use AI tools in your day-to-day engineering; the agentic SDLC isn’t a foreign concept to you but a target vision • Hands-on experience with LLM APIs in products: prompt design, structured outputs, tool use, and evaluation of model outputs • Experience with end-to-end development using Python (FastAPI or Django) and TypeScript/React/Next.js • Confident with PostgreSQL and schema migrations • Discipline in testing and CI (e.g. pytest, typed code, GitHub Actions or similar) • Experience with Docker-based deployment and a foundation in observability • Business-fluent English and ideally German at B1–B2 level This role probably isn’t for you if… This role is probably not the right fit if you only want to work on greenfield projects. Alongside building our new platform, you’ll also continue developing our existing learning framework, and both are equally part of the job. It’s also not a good fit if you see AI tools as a nice extra rather than something that fundamentally changes how we build software. And if internal tools appeal to you less than the big product, you probably won’t be happy here: the back office for Learning Coaches, Client Operations, and Sales is a central part of the role, and it’s often where you’ll feel your impact most quickly. What we offer Work culture A solution-oriented, data-driven way of working, an open feedback culture, and strong team spirit. Two Trustees, elected by the entire StackFuel team, act as a neutral, confidential point of contact for your questions and concerns. Ownership Take on responsibility from day one, actively contribute your own ideas, shape processes sustainably, and have a real influence on how we work. Hybrid working We work in a hybrid model and are usually in our Berlin office 3 days a week. Workation Work from anywhere in the EU, the EEA, and Turkey for up to 10 days per year. Room for exchange Regular team exchanges, seasonal celebrations, and an always well-stocked kitchen make for a lively atmosphere. Professional development Take our online trainings to expand your skills and become an expert in data and AI.