Grai

Senior Machine Learning Engineer (RecSys)

Grai

Warsaw, PolandFullTimePosted Jun 9, 2026

Job description

We are building an AI-powered music platform that’s transforming how people create, explore, and experience music. Our product leverages cutting-edge AI technologies to provide personalized music recommendations and unique features tailored to every music enthusiast. As we continue to grow, we’re looking for a Senior Machine Learning Engineer to design, build, and scale recommendation systems that deliver highly relevant, personalized experiences to our users.

You will work on large-scale user interaction data, develop retrieval and ranking models, and take them from experimentation to production. WHAT YOU’LL DO

  • Design and implement retrieval and ranking architectures for personalized recommendations
  • Work with large-scale user behavior and content data to extract meaningful signals
  • Build end-to-end ML systems: data processing, feature engineering, training, evaluation, deployment, monitoring
  • Run A/B tests and offline evaluations to measure model impact and guide improvements
  • Collaborate with product and engineering teams to align recommendations with business goals
  • Continuously monitor model performance WHAT WE’RE LOOKING FOR
  • Strong hands-on experience building recommendation systems or ranking models
  • Deep understanding of machine learning fundamentals and evaluation methodologies
  • Experience working with large-scale data (SQL, Spark, or distributed data systems)
  • Proficiency in Python and modern ML frameworks (Py. Torch, Tensor. Flow)
  • Understanding of core ML concepts: supervised/unsupervised learning, evaluation metrics, feature engineering
  • Experience deploying ML models to production and maintaining them over time
  • Ability to balance experimentation with production reliability NICE TO HAVE
  • Experience with real-time recommendation systems
  • Knowledge of search / information retrieval systems
  • Familiarity with feature stores, model monitoring, and ML infrastructure
  • Experience in media, music, or consumer-facing personalization products WHY JOIN US
  • Work on high-impact ML systems used by real users at scale
  • Ownership over meaningful technical decisions, from modeling to production
  • Collaborative, product-driven environment with strong engineering culture
  • A supportive and dynamic startup culture where your ideas and contributions truly matter
  • Opportunities for growth, learning, and shaping the future of our recommendation stack
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