Principal Applied Scientist / Lounge by Zalando (all genders)

Role: Lounge by Zalando is the leading online outlet in Europe, offering limited‑time exclusive discounts on premium fashion and lifestyle brands. As a Principal Applied Scientist you will work across two teams that build the customer‑facing fashion assistant and personalized landing pages, focusing on recommendation systems and agentic development. The role is an individual contributor position requiring strong coding skills and the ability to contribute to production‑grade software. Responsibilities: - Use LLM APIs to create the ideal fashion assistant for customers. - Develop and improve machine‑learning applications, such as personalized recommendation systems, to enhance browsing experience and communication. - Translate ambiguous business challenges into research questions, define solutions, and lead the end‑to‑end applied‑science strategy, including model selection, problem formulation, training and inference. - Develop and implement effective evaluation frameworks to assess impact, analyze customer behavior, and evaluate business performance. - Use AI coding tools to deliver software at a fast pace. Qualifications: - Strong expertise in production ML applications, with at least 3 years of hands‑on industry experience building and deploying scalable, high‑performance recommendation or search solutions. - Minimum 5 years of software engineering experience using Python. - Experience with LLM application development and evaluation (highly desired). - Excellent knowledge of machine learning and statistics, with a proven track record in addressing real‑world problems through empirical science, particularly online A/B testing. - Extensive hands‑on experience with deep learning, gradient‑boosting trees, vector search, preferably using libraries such as PyTorch, TensorFlow, CatBoost, FAISS. - Practical experience with large‑scale data processing and deploying ML models to production, especially for real‑time APIs (Databricks, Spark, Flink, Beam, SageMaker, Kubernetes, REST APIs). What We Offer: - 27 days of holiday per year (increasing up to 30 days with tenure). - 2 paid volunteering days per year. - Hybrid working model with up to 60 % remote work. - Ability to work from abroad for up to 30 working days per year. - Employee shares program. - 40 % discount on fashion and beauty products sold by Zalando, 30 % discount on Lounge by Zalando, plus external partner discounts. - Relocation assistance (subject to prior agreement). - Family services, counseling and support. - Health and wellbeing options, including Wellhub (formerly Gympass). - Mental health support and coaching. - Development opportunities through a training platform and bi‑annual peer‑to‑peer review.