Lead Data Science Engineer

Our client is a VC-backed startup building a web platform that helps people find jobs more effectively.
We’re looking for a Lead Data Science Engineer to lead the development of AI features across the platform. You’ll guide the DS/ML team and turn research into production solutions that directly improve the user experience.
Recommendation systems are the main focus. You’ll also work on classification, matching, structured data extraction, and AI agents for workflow automation.
You’ll work closely with Product and Engineering Leads to shape technical solutions, set quality standards, and grow the team’s capabilities.
This is a hands-on role. You must be able to write production code and deliver solutions end-to-end yourself, while leading the team through research, development, deployment, and ongoing improvement.

What you’ll own

• Technical direction for AI features. Build a roadmap with Product and choose approaches based on expected impact, evidence, and cost.
• Team leadership. Plan work, assign ownership, manage risks and dependencies, review code and experiments, mentor team members, and help hire as the team grows.
• Recommendations and personalisation. Improve retrieval and ranking using profile, content, and behavioural signals. Address cold start, incomplete data, changing preferences, freshness, and diversity.
• Applied ML and AI agents. Build classification, matching, extraction, and automation capabilities. Choose between traditional ML, LLMs, and simpler methods based on the problem.
• Data, research, and evaluation. Build reliable datasets and features, test hypotheses, and set clear quality standards. Validate labels, prevent leakage, account for behavioural bias, and connect offline evaluation with real user outcomes.
• Production delivery. Personally build and deploy models and services. Establish monitoring and release checks, resolve regressions, and balance quality with latency, reliability, and cost.

Required experience

• 5+ years of hands-on experience in Data Science / ML engineering, building and maintaining production solutions, including 2+ years leading a DS/ML team while remaining technically hands-on.
• Production experience with recommendation systems, including retrieval, ranking, personalisation, and behavioural signals.
• Personal experience deploying and operating ML models or services, including monitoring, troubleshooting, and rollback.
• Strong Python and SQL skills, with current experience writing maintainable production code.
• Practical knowledge of model training, feature engineering, embeddings, and classification.
• Experience with offline evaluation and A/B tests, connecting technical metrics to product results.
• Strong system design skills across data pipelines, training, inference, service integration, and scaling.
• Practical understanding of LLMs, their limitations, and how to evaluate their outputs.
• Independence and sound judgment: structure open-ended problems, explain trade-offs, challenge proposals, and drive work to a verified result.

Nice to have

• Experience with marketplaces or two-sided matching.
• Hybrid search, vector databases, and ANN indexes.
• Session-based recommendations and exploration strategies.
• Production experience with LLM agents, tool use, and structured extraction.
• Model distillation or active learning.

First 3 months expected outcomes

• Understand the platform’s AI features, data, evaluation methods, production constraints, and team.
• Take over technical leadership and day-to-day DS/ML delivery.
• Agree on a prioritised roadmap with Product and Engineering Leads, and start executing it with clear owners, milestones, and success criteria.

What the company offers

• Ownership of AI features used across the platform and room to grow your responsibilities.
• Direct influence on product decisions and user outcomes.
• Market-level compensation.
• Office/hybrid in Warsaw or Minsk, or fully remote from nearby time zones (CET ±2).
• 20 paid working days of vacation per year plus sick leave.

We look forward to receiving your CV and learning more about your experience!

Dear Candidates, due to a high volume of applications, only selected candidates will be contacted for interviews. We appreciate your understanding. Thank you for considering a career with us.