Lead Machine Learning Engineer – Recommendation Systems

The role

You will architect, build, and scale recommendation and discovery engines. You will own the technical roadmap for the RecSys stack to transform user behavior and social signals into personalized experiences.

What you will do

• Define the long-term technical vision and architectural roadmap for recommendation and personalization engines.
• Design and oversee the implementation of scalable retrieval, ranking, and re-ranking pipelines.
• Lead the development of robust ML infrastructure including automated data processing, feature stores, MLOps, and real-time model monitoring.
• Mentor and coach a team of ML engineers.
• Design offline evaluation frameworks and lead A/B testing strategies.
• Partner with Product and Engineering to align ML initiatives with business metrics and product goals.

Required qualifications

• Extensive experience designing, building, and scaling production-grade recommendation systems, search engines, or large-scale ranking models.
• Deep, foundational knowledge of machine learning, deep learning architectures, and modern information retrieval methodologies.
• Significant experience with distributed data systems and modern ML frameworks (PyTorch, TensorFlow).
• Proven ability to handle massive, high-throughput user interaction datasets.
• Strong background in deploying and maintaining low-latency models in production.
• Solid grasp of feature stores, model registries, and drift monitoring.
• Demonstrated experience leading technical projects, mentoring engineers, and managing stakeholders.

Nice to have

• Experience with streaming data architectures and real-time/session-based recommendation systems.
• Background in audio processing, music streaming, or high-growth consumer-facing personalization products.
• Familiarity with graph neural networks (GNNs), reinforcement learning, or leveraging Large Language Models (LLMs) for recommendation context.

Benefits

• Meaningful stock options
• 26 business days of paid time off per year
• 5 days off
• Polish public holidays

About the company

GRAI is a social music app out of Warsaw, currently in alpha. They are building new ways to listen and respond through music.