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

💚 Your benefits at Kleinanzeigen 

At Kleinanzeigen, we care about our people — their wellbeing, growth, and life beyond work. Our benefits are designed to support you holistically, giving you flexibility and opportunities to thrive.

✨ Flexibility

• Flexible working time (hybrid)

• 20 days “work from anywhere”

• Paid additional parental leave for both parents

• Extra paid days off for special occasions (e.g. your wedding or a move)

❤️‍🩹 Wellbeing & Support

• Confidential support & coaching for you and your loved ones

• Annual company sports events

• Pension and life insurance

📚 Growth & Development

• Personal development budget

• Learning opportunities to grow your skills and career

🛍️ Perks & Everyday benefits

• Corporate benefits and exclusive discounts

• An attractive referral program 

• Transportation allowance

• Free shipping on Kleinanzeigen Direktkauf

Kleinanzeigen is an equal opportunity employer that values diversity and inclusion. We welcome people of all backgrounds, races, religions, colours, national origins, gender identities, sexual orientation, ages, marital status, or disability.

If this role sparks your interest but you’re not sure you meet every single requirement, we’d still love to hear from you anyway. 

As Principal Backend Engineer – AI Engineering & Architecture, you will own the implementation and evangelization of AI-First Engineering across Kleinanzeigen. You will work without a fixed team, operating across all engineering units with the authority and accountability of a senior organizational leader.
AI Strategy & Standards

• Define and operationalize AI-First engineering practices across the entire engineering organization — from Intent Specification frameworks to CLAUDE.md/AGENT.md standards for every repository.
• Drive the transition from Level 1 (Assisted) to Level 2 (Agentic) AI maturity, and architect the foundations for Level 3 (Orchestrated) — where engineers coordinate multiple specialized agents working in parallel.
• Own and evolve the organizational context layer: mandatory machine-readable operating contexts (CLAUDE.md, AGENT.md) that give AI tools the architectural constraints and conventions they need to generate trustworthy output.
• Measure and report on AI adoption progress using the DX Core 4 framework, targeting p75 as the minimum benchmark and p90 (DXI ≥ 80) as the inspirational goal.

Architecture Board Co-Leadership

• Co-lead the Kleinanzeigen Architecture Board (KAB) — the governing body responsible for defining AI's impact on the SDLC, setting security guardrails, and publishing the AI security and data classification policies.
• Define and enforce interim and permanent guardrails for AI-generated code, including mandatory security-focused review for code touching authentication, payments, or PII.
• Lead the Fast Forward initiative — the proposed vehicle for advancing AI capabilities within a governed engineering framework — from concept to organizational reality.
• Design scalable, resilient systems (up to 60k req/s) and drive architecture evolution from problem definition to production, making and clearly justifying trade-offs at organizational scale.

Evangelization & Culture Change

• Partner with Engineering Managers to embed AI capability expectations into team practices, retrospectives, and planning conversations — making 'Why wasn't AI used here?' a normal part of engineering culture.
• Pair skeptical engineers with AI-fluent colleagues on high-value legacy challenges — large-scale refactors, documentation backfills, migration tasks — to demonstrate productivity gains through example rather than mandate.
• Contribute to updating hiring standards: formalizing the AI-assisted profile as the expected standard for engineering candidates, incorporating the AI-dependent / AI-assisted / AI-resistant distinction into the Skill Framework.
• Model AI-First engineering visibly in your own work, setting the standard for the broader organization.

Tooling & Infrastructure

• Collaborate with DevEx on the AI developer experience layer: tooling implementation, the Skill Library, and productivity measurement.
• Collaborate with AI Enablement on the orchestration framework and agentic stack: the runtime for AI agents, multi-agent coordination, and context management infrastructure.
• Leverage and help standardize world-class AI tooling, including Claude Code, across the engineering organization.

WHAT THIS ROLE IS NOT
This is not a management role. You will not have direct reports. But you will be expected to change how over 200 engineers work. That requires more influence than authority — which means you need to be technically credible, organizationally fluent, and genuinely energized by the challenge of moving a large engineering organization through a structural transition.
This is also not a research role. We are not looking for someone to study AI trends. We are looking for someone who will implement, evangelize, and measure — someone who is equally comfortable writing an architecture proposal, running a pairing session on Belen, and presenting to the Tech LT.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. We are at a pivotal moment: not just growing, but changing the fundamental structure of how we build software.
This is not a team role. 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. 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.
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.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.
• Proven ability to operate effectively without a fixed team context — you are energized by ambiguity, organizational influence, and cross-functional work.
• 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.
• Familiarity with legacy codebase modernization — you understand the specific challenges of working on and around large, active monoliths.
• 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.