Senior Data Scientist Reinforcement Learning – Offer Intelligence (m/f/d)

Sixt-; Lisboa; Hybrid; EUR 70,000 - 110,000; Full time

Benefits offered by this job

Global tech hub in Lisbon

Learning & Knowledge Exchange

Flexible work setup

Time off & wellbeing

Practical everyday benefits

SIXT perks

Job summary

Sixt Research Development Services, Lda. in Lisbon is seeking a data science professional to architect Bayesian pricing models and scalable personalisation systems. You will own end-to-end model lifecycle, from problem framing to live deployment, with a focus on robust decision-making under uncertainty.

The role emphasizes production-grade Python, CI/CD practices, and collaboration with product, revenue, and customer teams to translate ideas into testable hypotheses.

Qualifications

• Expertise: You bring deep statistical chops, with 5+ years of applying regression, hierarchical models, or state-space methods in production
• Computing: 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
• 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

Responsibilities

• Architect and prototype advanced regression models with a principled Bayesian approach, guiding pricing at scale
• Design and productionise personalisation and recommendation systems with two-tower retrieval and learning-to-rank
• Apply techniques like SVI, MCMC, and importance sampling for robust decision-making
• Build and maintain reproducible pipelines for feature engineering, label generation, and automated data validation (Airflow/Dagster)
• Deploy models via FastAPI, Docker, or Kubeflow; establish real-time monitoring and dashboards
• Design sophisticated A/B and causal tests; mentor peers and elevate Bayesian practice

Skills

Regression modeling

Bayesian statistics

Python programming

Uncertainty communication

Collaboration

Tools

PyMC

Stan

NumPyro

TFP

Airflow

Dagster

FastAPI

Docker

Kubeflow

Job description

• Full-time
• Legal Entity: Sixt Research Development Services, Lda.

Job Description

We 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

Additional Information

About us:

We are a globally leading mobility service provider with a revenue of €4.3 billion and around 9,000 employees worldwide. Our mobility platform ONE combines our products SIXT rent (car rental), SIXT share (car sharing), SIXT ride (taxi, ride, and chauffeur services), and SIXT+ (car subscription), giving our customers access to our fleet of 360,000 vehicles, the services of 4,000 cooperation partners, and around 5 million drivers worldwide. Together with our franchise partners, we are present in more than 100 countries at 2,000 rental stations. At SIXT, top-tier customer experience and outstanding customer service are our highest priorities. We believe in true entrepreneurship and long-term stability and align our corporate strategy with foresight.