Principal Backend Engineer AI Engineering & Architecture (d/f/m)

Das ist der Job

We are at a pivotal moment: not just growing, but changing the fundamental structure of how we build software.

Darum lohnt es sich

This is not a team role. Integrating AI-First practices across a codebase of this size and complexity, while simultaneously evolving our architecture toward modern distributed systems, is not a problem that solves itself.

Proven ability to operate effectively without a fixed team context — you are energized by ambiguity, organizational influence, and cross-functional work. Familiarity with legacy codebase modernization — you understand the specific challenges of working on and around large, active monoliths.

Description Kleinanzeigen is Germany's most-visited classifieds platform — over 50 million items, 35 million unique monthly users, and roughly 50% of the German internet population reached. It is one of the most consequential individual-contributor positions we are opening as we enter a period of genuine disruption in software engineering.

You will report directly to the Head of Engineering, co-lead our Architecture Board, and carry a mandate that spans every engineering unit in Kleinanzeigen. Your mission is to make AI-First Engineering real — not as a banner, but as a durable change in how over 200 engineers design, build, and own software.

The disruption of AI is not about productivity. It is about the cost structure and identity of software engineering. You will lead that transition. CONTEXT: WHERE WE ARE AND WHERE WE ARE GOING We have invested in world-class AI tooling and built the early foundations for AI-assisted engineering.

Adoption is growing, and the signal is clear: this is working. Now we are ready to move from early adoption to organization-wide transformation — and that shift requires more than enthusiasm. It requires deliberate engineering leadership.

Our platform runs at scale — tens of millions of users, high traffic, and a significant body of production systems built over many years. We are also at an inflection point as an organization: expanding across geographies and raising our technical ambition in parallel.

AI adoption lands on top of this, which makes it both harder to execute and more important to get right. This is the context you will be operating in — and the reason this role exists. Requirements Required 8+ years of backend engineering, primarily in Java — strong knowledge of Java Core APIs, Spring Framework, and Spring Boot.

Proven experience designing and operating robust, scalable distributed systems, ideally on public cloud (AWS with Kubernetes). Strong knowledge of event-driven systems (e.g. Kafka) and solid experience with RDBMS and NoSQL (MySQL, Cassandra, Elasticsearch preferred).

Demonstrated, hands-on experience with AI-assisted development tools (Claude Code, Copilot, Cursor, or equivalent) — you use these tools daily and can articulate their trade-offs clearly. Strong written and verbal communication: you can write a compelling architecture document, run a workshop, and present clearly to senior leadership.

Experience with architecture review processes, governance frameworks, or engineering standards definition. Strong engineering fundamentals: Domain-Driven Design, Clean Code, and a deep understanding of architectural trade-offs. Strong Advantage Experience building or operating AI agents or multi-agent systems.

Familiarity with DORA, SPACE, DX Core 4, or similar developer productivity measurement frameworks. Experience in large-scale engineering transformation or organizational change in a technical context. Experience in classifieds, marketplace, or high-traffic consumer platform engineering.

Profile You have a speak-up mentality and are comfortable pointing out what is not right — including in rooms with more seniority than you. You distinguish clearly between AI-assisted engineering (the target) and AI-dependent engineering (not acceptable). You are as comfortable in a codebase as in a strategy document.

You believe the new craft of engineering is the ability to translate vision into precise intent and orchestrate AI toward correct outcomes — and you are excited to teach it.