Lead Fullstack Engineer (f/m/d)

Your Mission

As Lead Fullstack Engineer at hallo theo, you design, build and operate the core systems of our AI-native property management platform. You work hands-on across the stack – from intuitive frontends to robust backend services and data flows – and take real ownership for critical user journeys. You work with great attention to detail, empathy and a solution-oriented mindset, with a strong feel for both our users and our technology, and you help turn ambiguous problems into simple, impactful product experiences.

Your Responsibilities

• Own the end-to-end delivery of features and services – from discovery and technical design through implementation, testing, rollout and monitoring in production.
• Build and evolve reliable backend and frontend components (APIs, services, UIs) that integrate with our web tech stack and data layer.
• Improve our architecture and codebase: refactor, define clear interfaces and keep our platform secure, observable and maintainable.
• Collaborate closely with Product, Design and Operations to shape scope, break down complex problems and make pragmatic trade-offs between speed and quality.
• Act as a technical sparring partner and mentor for other engineers, supporting good engineering practices and a healthy engineering culture.

Preferred Background

• 6–8 years of experience in software engineering, ideally in product-driven environments (startups, scale-ups or similar), with a strong track record in complex and uncertain projects.
• Strong product mindset: you think in user journeys and outcomes, not just tickets, and you are comfortable making trade-offs under ambiguity.
• Solid understanding of LLMs, RAG and current AI trends, and motivation to apply them pragmatically in a real product.
• Proficient in at least one modern programming language and experienced in a web tech stack (e.g. Python and SQL, plus modern web frameworks and APIs).
• Experience operating services in the cloud (e.g. AWS, GCP or Azure), including CI/CD, logging, monitoring and basic security practices.
• Business-fluent German (C1 or higher) and strong English skills, as you’ll work with German-speaking stakeholders and an international team.

Nice to have

• Experience in domains with complex operations or workflows (e.g. proptech, fintech, marketplaces or B2B SaaS).
• Prior experience in a “tech lead” capacity (leading projects or streams), even without formal line management. Why Join Us

At hallo theo, you work on AI with real impact: we are not just building tools, we are reshaping the everyday reality of millions of people who live in and manage properties. You’ll join an interdisciplinary team of experts from real estate, tech and operations and help define how modern AI products are built and run in our industry. With a clear, ambitious vision and a tech- and AI-first operating model, you’ll have the autonomy and responsibility to shape our platform, our engineering practices and the future of property management in Germany.