Senior Fullstack AI Engineer (f/m/d)

StackFuel GmbH; Berlin; On-site; EUR 90,000 - 130,000; Full time

Benefits offered by this job

Hybrid working

Workation in EU/EEA/Turkey

Berlin office access

Professional development

Job summary

StackFuel GmbH in Berlin is building a next-generation adaptive learning platform with an AI-first approach from the ground up. You will shape the platform from database to frontend, impacting thousands of learners across German companies.

As a Senior Fullstack AI Engineer, you’ll own end-to-end development, drive architectural choices, and implement AI features such as LLM-powered support and adaptive learning paths, while collaborating across teams and mentoring peers.

Qualifications

• 5+ years of experience in full-stack development with senior responsibilities (architecture, mentoring).
• AI-first mindset; daily use of AI tools and an agentic SDLC target.
• Experience with Python and TS/React/Next.js; PostgreSQL; testing and CI.

Responsibilities

• Develop the adaptive, AI-first learning platform end-to-end and make key architecture decisions.
• Implement new features in the learning framework and balance new development with improvements.
• Build AI features into the platform (LLM-assisted learning, adaptive paths, content generation) with reliable, cost-efficient operation.
• Create internal tools and AI automations for Learning Coaches, Client Operations, and Sales.
• Collaborate with the engineering team, Content Engineering, and Portfolio Leads.

Skills

Full-stack dev

AI-first development

LLM APIs

Python (FastAPI/Django)

TS/React/Next.js

PostgreSQL

CI/CD

Docker

Observability

English/German

Tools

GitHub Actions

Docker

PostgreSQL

Job description

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.