Refinery89 is looking for an experienced and highly analytical Senior Data Scientist to join our growing AI and Data team. If you’re passionate about building intelligent systems that drive real business impact, thrive on solving complex problems, and want to shape the future of AdTech innovation — we want to meet you.

What You’ll Do:

• Lead the development of advanced statistical and machine learning models to optimize key performance parameters across our platforms (timeouts, refresh rates, ad placement logic, etc.).
• Design and execute A/B/n experiments to test multiple parameter configurations simultaneously, driving measurable improvements in system efficiency and revenue outcomes.
• Translate data and experimentation results into scalable, production-ready solutions that integrate seamlessly with our product and engineering teams.
• Collaborate with cross-functional stakeholders — from Product to Commercial — to identify high-impact use cases and align technical outcomes with strategic goals.
• Own the end-to-end lifecycle of models: from ideation, data wrangling, development, and deployment, through to performance monitoring and optimization.
• Present complex findings in a clear and actionable way to both technical and non-technical audiences.

Who We're Looking For:

• Experienced Problem Solver: 5+ years in data science or machine learning roles, ideally in fast-paced digital or AdTech environments.
• Advanced Technical Proficiency: Strong in Python and SQL, with proven experience in statistical modeling, experimentation, and ML libraries (e.g., scikit-learn, TensorFlow, PyTorch).
• Cloud Native: Familiarity with cloud environments such as AWS or Azure, including experience deploying models in cloud infrastructure.
• Experimentation Expert: Hands-on experience designing, running, and analyzing A/B and multivariate tests with robust statistical rigor.
• Communicator & Collaborator: You’re equally comfortable in code and in a boardroom. You can explain complex results to a CRO, and architecture decisions to an engineer.
• Business-Oriented Thinker: You understand that the success of an algorithm is not only in its accuracy but in its impact on product and revenue metrics.

Nice-to-Haves:

• Background in AdTech, programmatic advertising, or digital publishing.
• Experience with LLMs, causal inference, or real-time prediction models.
• Exposure to tools like Airflow, Docker, or Spark in a production context.

What You Can Expect from Us:

• Competitive salary package tailored to your experience.
• Bonus structure tied to impact and performance.
• Remote-first flexibility with access to a beautiful 800m² office in central Madrid (Cuatro Caminos).
• 24 holidays per year, your own equipment, and weekly Friday half-days.
• A flat, fast-moving, and feedback-friendly culture — inspired by our Dutch roots.
• Annual team retreat and regular knowledge-sharing sessions with our international team.
• A chance to work on real business problems, build impactful AI systems, and push the boundaries of what's possible in AdTech.
  
  
  Ready to bring science to strategy and shape the future of advertising?
  Apply today and let’s shape the future of programmatic advertising together! 🚀