Senior Data Scientist - Reinforcement Learning and Offer Intelligence

Job DescriptionWe work at the intersection of pricing science, offer personalisation, advanced statistics, and scalable software. You'll build and bring into production state-of-the-art probabilistic models - like hierarchical Bayesian regression, SVI, or bandit algorithms - that power millions of pricing and offer decisions at SIXT every day. Beyond pricing, we're building the intelligence layer that decides which offer and which experience each customer sees, so your models shape both what we charge and what we show. From shaping the analytical question to deploying live models, you'll own the full lifecycle, supported by an innovation-friendly culture and great team. If you're excited by real-world impact, rigorous methods, and turning cutting-edge ideas into production - even if you don't tick every box - we'd love to hear from you! YOUR ROLE AT SIXT You architect and prototype advanced regression models (linear, GLM, mixed-effects, Gaussian Process) with a principled Bayesian approach, guiding pricing strategy at scale You design and productionise personalisation and recommendation systems - two-tower retrieval, embedding-based candidate generation, learning-to-rank, sequential/transformer models - with contextual bandits and off-policy evaluation to keep them learning from real interactions You apply techniques like SVI, MCMC, and importance sampling to enable robust decision-making under uncertainty, even with sparse, high-volume, or streaming data You build and maintain reproducible pipelines for feature engineering, label generation, and automated data validation using tools like Airflow or Dagster, ensuring high code quality and reliability You deploy models via FastAPI, Docker, or Kubeflow, and establish real-time monitoring with Bayesian control charts and performance dashboards to catch drift and anomalies early You design sophisticated A/B and multivariate tests, apply quasi-experimental and causal impact methods, and quantify the value of information to balance exploration and exploitation You collaborate with product, revenue, and customer experience leaders to translate ambiguous ideas into testable hypotheses, while mentoring peers and elevating Bayesian practice through internal publications and workshops YOUR SKILLS MATTER Expertise You bring deep statistical chops, with 5+ years of applying regression, hierarchical models, or state-space methods in production Computing proficiency You have a well-stocked Bayesian toolbelt - fluent in PyMC, Stan, NumPyro, TFP, or similar - and are comfortable writing custom likelihoods and priors. Modeling You have proven experience scaling inference using SVI, black-box VI, or advanced MCMC techniques on large datasets Personalisation (nice to have) You have experience with recommender and personalisation stacks - two-tower / embedding retrieval, learning-to-rank, sequential models, contextual bandits - plus counterfactual or off-policy evaluation to prove incremental value rather than optimise click-through Engineering practices You write solid, production-grade Python code and are familiar with type hints, testing frameworks, and CI/CD workflows Infrastructure You are hands-on with cloud platforms like AWS, GCP, or Azure, and have experience with containerization (Docker/K8s) and workflow orchestration Stakeholder management You communicate uncertainty, lift, and risk in plain English for executives, while engaging deeply with scientists and engineers WHAT WE OFFER A Global Tech Hub in Lisbon Join a thriving international tech community and work alongside engineers, product experts, and business teams who turn ideas into real impact. Our hubs at Factory Lisboa in Beato and ARTs Lisboa in Parque das Nações are where great tech gets built Learning & Knowledge Exchange Level up through regular events with internal and external speakers. We value curiosity, continuous learning, and open exchange – across teams, disciplines, and borders Flexible Work Setup Two office days a week, flexible hours, and modern spaces built for both deep focus and team collaboration – work the way that brings out your best Time Off & Wellbeing Enjoy 28 vacation days per year, an additional day off on your birthday, one volunteer day annually, and private health insurance that also covers your spouse and children free of charge Practical Everyday Benefits Get a yearly Coverflex allowance and a daily meal allowance to make everyday life a little easier SIXT Perks Get exclusive rates on all SIXT services, with special discounts extended to your family and friends. Because great perks are even better when you can share them