Senior Data Scientist (Recommender Systems)

Location: Hybrid in Berlin, Germany; Tallinn, Estonia; or Bucharest, Romania. The role also includes on-site work at the Tallinn headquarters.

Company

Bolt is a technology company operating mobility and delivery products across more than 50 countries and 850+ cities, including Bolt Food.

What you will do

• Improve ranking and recommendation systems for the Bolt Food home screen and other personalized surfaces.
• Build learning-to-rank, personalized recommendation, cold-start, exploration, and screen-assembly solutions.
• Help customers discover restaurants, stores, dishes, and items while balancing relevance with business objectives and guardrails.
• Design and run A/B tests and evaluate ranking and personalization changes using offline and online metrics.
• Take machine-learning models from research through production with Product, Engineering, Analytics, and ML Platform teams.
• Shape technical direction for candidate generation, features, logging, experimentation tooling, and emerging sequential or generative recommenders.

Requirements

• 5+ years of experience in Data Science and Machine Learning, preferably building products at a technology company.
• Hands-on experience with large-scale ranking, recommender, or personalization systems.
• Strong Python and SQL skills, plus experience with PyTorch, Pandas, NumPy, and scikit-learn.
• Experience with several techniques including learning-to-rank, collaborative filtering, two-tower or sequential models, embeddings, vector search, gradient boosting, or multi-objective optimization.
• Strong knowledge of experimentation, statistical inference, offline and online evaluation, and product-oriented problem solving.
• Experience building ML systems end to end and driving projects from problem discovery to production impact.

Nice to have

• Search and information retrieval experience.
• Experience with sequential and generative recommender systems.

Culture & Benefits

• Inclusive workplace with equal-opportunity hiring and reasonable accommodations.
• Professional growth opportunities and annual company events.
• Salary, stock options, and physical and mental wellness benefits.
• A one-month paid sabbatical after five years at Bolt.
• Daily use of AI coding tools is encouraged, with responsibility for the quality of the output.