Senior Data Scientist - Rankings & Recommendations (all genders)

You'll join Search Intelligence, the team behind Holidu's ranking and recommendation systems. With over 8 million vacation rental properties on the platform, your models will determine which of them our 70+ million annual users discover first — directly shaping search conversion and business results. It's one of the highest-leverage problems in the company — and we're not just maintaining a finished system: we're pushing the boundaries of what search at Holidu can do. You'll work with a large and rich dataset, fast paths from concept to production, and the autonomy to act on your own judgment.

Holidu is an AI-first company, and it shows in how we work: your modelling stays grounded in machine learning and statistics, but you'll have large-scale access to the best AI tools and the freedom to weave them into everything you do — from discovery to implementation to maintenance. Everyone here experiments and shares what works, and we'll count on you to help push how far AI can take us.

This role is based in Munich with two office days/week.

The ranking challenge at Holidu

Ranking at Holidu is already a deep system: a multi-stage pipeline with reinforcement-learning-based cold ranking, contextual re-ranking, and personalized recommendations, plus dedicated cold-start models for new properties with limited behavioral data. And it keeps expanding — we're starting to enrich our models with AI-generated semantic signals that describe what makes each home special, opening the door to smarter ranking and entirely new search experiences.The next generation of it is yours to figure out. 

Some of the hard challenges we're tackling: balancing user relevance, conversion probability, and business value in a single ranking. Personalizing for users who are mostly anonymous or first-time visitors. Surfacing great new properties before any behavioral data exists — when a significant share of our inventory is new each quarter. And adapting our ranking to evolving partner and business models, where the right answer changes as the marketplace does.

Python • Airflow • dbt • AWS (SageMaker, Redshift, Athena) • MLflow

You'll shape the ranking and recommendation systems that millions of guests rely on end-to-end. You will:

• Develop high-impact models and improvements for our ranking, recommendation, and personalization systems — with the freedom to explore new, creative approaches.
• Take models from conception to production, monitor their performance, and iterate to enhance accuracy and efficiency.
• Design and run A/B tests as a core part of ranking development — ship experiments fast, learn from real traffic, and let winning ideas go live.
• Collaborate closely with Product Managers and Software Engineers to identify, prioritize, and ship ranking improvements.
• Ensure model reliability in production — online/offline agreement, drift KPIs, latency and uptime SLAs, and automated monitoring.
• Take the technical lead on projects by driving direction, scoping initiatives, and guiding prioritization.
• Continuously fold AI into how you work — finding smarter, faster ways to build, experiment on, and maintain your systems and workflows.

• 3+ years of experience as a Data Scientist with a proven track record of applying ML models to solve real business problems.
• Experience with ranking models or recommender systems is a strong advantage.
• A quantitative degree in Machine Learning, Computer Science, Mathematics, Physics, or a related field.
• Strong foundations in statistics, predictive modelling, and machine learning, with hands-on experience in Python and SQL.
• Hands-on experience with tree-based and gradient-boosting models (XGBoost, LightGBM, CatBoost) on large-scale tabular data.
• A proactive, self-starting mindset — you love to own a domain and shape it end-to-end.
• Genuine enthusiasm for using AI in your daily work — you experiment, adopt what works, and help move the boundaries of its usage.

• Impact: Shape the future of travel with products used by millions of guests and thousands of hosts. At Holidu ideas become products, data drives decisions, and iteration fuels fast learning. Your work matters - and you’ll see the impact.
• Learning: Grow professionally in a culture that thrives on curiosity and feedback. You’ll learn from outstanding colleagues, collaborate across disciplines, and benefit from mentorship, and personal learning budgets - with a strong focus on AI.
• Great People: Join a team of smart, motivated and international colleagues who challenge and support each other. We celebrate wins and keep our culture fun, ambitious and human. Our customers are guests and hosts - people we can all relate to - making work meaningful and energizing.
• Technology: Work in a modern tech environment. You’ll experience the pace of a scale-up combined with the stability of a proven business model, enabling you to build, test, and improve continuously.
• Flexibility: Work a hybrid setup with 50% in-office time for collaboration, and spend up to 8 weeks a year from other inspiring locations. You’ll stay connected through regular events and meet-ups across our almost 30 offices.
• Perks on Top: Of course, we also offer travel benefits, gym discounts, and other perks to keep you energized - but what truly sets us apart is the chance to grow in a dynamic industry, alongside amazing people, while having fun along the way.