Senior Data Scientist - Rankings & Recommendations (all genders)

Your future teamYou'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 HoliduRanking 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. Our Tech StackPython • Airflow • dbt • AWS (SageMaker, Redshift, Athena) • MLflow  Your role in this journeyYou'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. Your backpack is filled with3+ 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 boun