Senior Applied Scientist - Lounge by Zalando (all genders)

THE ROLE AND THE TEAM

As a Senior Applied Scientist in the Assortment Optimization team at Zalando Lounge, you will build machine learning and optimization products that improve one of our most critical levers: buying decisions. Your work will help determine what we buy, how much we buy, and how we holistically optimize Lounge’s assortment - with direct impact on key long-term business outcomes.

This role is ideal if you enjoy turning complex, constraint-heavy problems into scalable decision systems. You'll work end-to-end, from framing the business problem and designing the modeling and optimization approach, to deploying reliable solutions that are used in everyday buying workflows.

Importantly, algorithmic-driven buying in Lounge is still an emerging field: there is substantial white space to explore, new decision products to invent, and foundational capabilities to build. That means a rare chance to shape the direction of the domain and deliver outsized business impact early.

You will collaborate closely with Applied Scientists, Software Engineers, and commercial stakeholders to deliver decision-support solutions that are actionable, explainable, well evaluated and production-ready.

INCLUSIVE BY DESIGN

At Zalando, our vision is to be the leading pan-European ecosystem for fashion and lifestyle e-commerce – one that thrives on diversity and is truly inclusive by design. We believe that diverse teams fuel innovation and creativity, and we actively seek out talent from all backgrounds.

We actively seek to reduce bias in our hiring and employment processes, focusing on your qualifications, skills, and contributions. To support this, we kindly ask that you refrain from including personal details such as your photo, age, or marital status in your CV, ensuring a fair and equitable evaluation based solely on your abilities and potential.

We are committed to providing an exceptional and accessible candidate experience for everyone. If you require any accommodations to support you throughout the hiring process, please let us know – we are here to assist you.

Discover more about our commitment to creating a diverse and inclusive workplace:

WHAT WE’D LOVE YOU TO DO (AND LOVE DOING)

Design and develop forecasting and optimization models that improve buying decisions (e.g., buy quantity recommendations, assortment selection, budget allocation).

• Own the full applied science lifecycle: ML system design, data exploration, feature engineering, model/optimizer development, evaluation, deployment, monitoring, and iteration.
• Translate business goals and constraints into objective functions and model design
• Build solutions that are production-ready, following software engineering best practices (testing, CI/CD, code quality, reproducibility, monitoring).
• Partner with engineers to ensure scalable implementations and reliable integration into business workflows.
• Proactively identify opportunities to improve the buying decisions and contribute to the product roadmap with high-impact ideas.

WE'D LOVE TO MEET YOU IF

• You have 3+ years of experience building applied ML and optimization solutions in a business environment.
• You are strong in Python and comfortable writing production-quality code (tests, clean architecture, CI/CD mindset).
• You have solid foundations in machine learning, mathematical optimization and statistics (e.g., regression, classification, uncertainty estimation, causal thinking is a plus) and are an expert in one of them.
• You have experience with common ML libraries such as scikit-learn, CatBoost/XGBoost/LightGBM, PyTorch/TensorFlow, and strong data tooling skills (e.g., pandas, numpy).
• You can communicate clearly with both technical and non-technical stakeholders and enjoy turning ambiguous problems into actionable solutions.
• Experience in optimization / operations research (e.g., linear/integer programming, constrained optimization, heuristics, simulation) with tools like OR-Tools, Pyomo, Gurobi, or similar is a plus.

WHY THIS ROLE

• Shape core buying decisions and drive measurable commercial outcomes, with your work having direct visibility and impact on the business.
• Own solutions end-to-end from research and prototyping through production, ensuring they are adopted and used in daily workflows.
• Work in a strong cross-functional, product-oriented environment alongside Applied Scientists and Software Engineers to build scalable decision tools.

OUR OFFER

Zalando provides a range of benefits, here’s an overview of what you can expect. Ask your Talent Acquisition Partner to learn more about what we offer.

• 27 days of holiday a year to start for full-time employees (+1 day for every calendar year up to 30 days)
• 2 paid volunteering days a year
• Hybrid working model with up to 60% remote per week, actual practice is up to each team to best support their collaboration
• Work from abroad for up to 30 working days a year
• Employee shares program
• 40% off fashion and beauty products sold and shipped by Zalando, 30% off Lounge by Zalando, discounts from external partners
• Relocation assistance available (subject to prior agreement)
• Family services, including counseling and support
• Health and wellbeing options (including Wellhub, formerly Gympass)
• Mental health support and coaching available
• Drive your development through our training platform and biannual peer-to-peer review

ABOUT LOUNGE BY ZALANDO

Lounge by Zalando is an online outlet for fashion and lifestyle products in 20+ European countries. We offer our members daily, time-limited sale campaigns with discounts of up to 75% off the recommended retail price. However, Lounge by Zalando is so much more than discounts. Our strength lies in our focus on fashion and lifestyle brands: from sought-after labels to niche brands, from famous international names to trendy luxury brands, we make sure to meet the fashion taste of all our customers, who are always on the hunt for the best products at the best prices. Working with our brand partners, we're pioneering innovative supply-chain and production processes and offer them an impactful and smart solution, creating a new way to shop for fashion - and a new way to sell it.