Data Science Expert

Playtika; Warszawa; On-site; PLN 260,000 - 380,000; Full time

Job summary

Playtika in Warsaw, Poland, is seeking a Data Scientist Expert - Production ML to join the Data & AI department. You'll advance real-time personalization using Bayesian methods, scale models to millions of players, and own end-to-end improvements from research to production.

The role emphasizes independent problem finding, collaboration with engineers, BI, and product teams, and mentoring others, with a focus on statistical rigor and deploying impactful ML in production.

Qualifications

• M.Sc or PhD in Computer Science, Mathematics, Statistics, Engineering or a related field.
• 5+ years of relevant working experience, including significant production ML ownership.
• Experience taking statistically sophisticated models from prototype to production and operating them under real-world constraints.
• Experience with neural network architectures and diagnosing their behavior in probabilistic or decision-making contexts.
• Strong foundation in Multi-Armed Bandits, Bayesian methods, online learning, or related decision-making frameworks.
• Strong understanding of experimentation, causal inference and online decision systems evaluation.
• Proficiency in Python for production-grade code and SQL.
• Ability to communicate statistical reasoning to non-technical stakeholders.

Responsibilities

• Identify limitations in existing ML solutions and deliver provably correct, more efficient alternatives.
• Validate correctness of scaled solutions and redesign as needed for distributed execution.
• Own the full lifecycle of improvements from research to production deployment and impact measurement.
• Drive evolution and scalability of personalization and recommendation systems.
• Contribute to end-to-end data-driven research including problem definition, data collection, model development, evaluation, and deployment.
• Collaborate with engineers, BI, and Product to deploy solutions quickly and effectively.
• Mentor Data Scientists and ML Engineers and provide a technical reference on statistical and mathematical rigor.

Skills

Python

SQL

Bayesian methods

Reinforcement learning

NN architectures

Production ML ownership

Education

MSc or PhD in CS/Math/Stats/Engineering

Tools

PyBandits

PySpark

PyMC/NumPyro

MLOps / model serving

Claude/Cursor AI tools

Job description

Ambition Needs a Place to Grow.At Playtika, we create mobile games enjoyed by millions worldwide.

Ambition Needs a Place to Grow.At Playtika, we create mobile games enjoyed by millions worldwide. Combining the scale of a public company (NASDAQ: PLTK) with the speed and ownership of a startup, we are a global leader where innovation, data, and creativity shape the future of entertainment. Here, your ideas matter, your decisions impact products, and your growth is supported across global studios. Bring your hunger where it belongs: at the front of the pack. Playtika is looking for a Data Scientist Expert - Production ML to join the Data & AI department In this position you will join a multidisciplinary team focused on personalization using Reinforcement Learning methods. Over the last few years, we have built a real-time recommendation engine based on Bayesian Multi-Armed Bandits - including our open-source PyBandits library - serving millions of players across multiple studios and use-cases. This is an applied research role, with impact measured in production. Your primary contribution will be advancing the mathematical and statistical foundations of our existing solutions: identifying limitations, deriving principled improvements, and owning those improvements all the way through to production. You will not be handed research problems from above - you will find them yourself, inside systems that are already running at scale. Scaling here is fundamentally a mathematical problem: identifying better statistical methods, proving they hold under real-world constraints, and knowing exactly how far they deviate from the ideal. That's what sets this role apart. Responsibilities:

• Identify mathematical and statistical limitations in existing ML solutions and deliver provably correct, more efficient alternatives
• Validate the correctness of scaled solutions - diagnosing where distributed execution or approximation invalidates prototype-level results, and redesigning accordingly
• Own the full lifecycle of your improvements: from research and prototyping through production deployment and impact measurement
• Drive the evolution and scalability of our personalization and recommendation systems to meet future business and technical requirements
• Contribute to end-to-end data-driven research including problem definition, data collection, model development, evaluation, and deployment
• Collaborate with cross-functional teams (engineers, BI, Product) to deploy solutions quickly and effectively
• Mentor Data Scientists and ML Engineers, and serve as a technical reference on statistical and mathematical rigor across the organization

Requirements:

• M.Sc or PhD in Computer Science, Mathematics, Statistics, Engineering or a related field
• 5+ years of relevant working experience, including significant production ML ownership
• Demonstrated experience taking statistically sophisticated models from prototype to production and operating them successfully under real-world business constraints.
• Experience with neural network architectures, including the ability to diagnose, interpret and debug their behavior in probabilistic or decision-making contexts (e.g. Bayesian Neural Networks, Neural Linear models)
• Strong theoretical foundation in at least one of: Multi-Armed Bandits, Bayesian methods, online learning, recommendation systems, or related decision-making frameworks
• Strong understanding of experimentation, causal inference and statistical evaluation of online decision systems.
• Strong hands-on Python engineering skills, with the ability to design, implement, review, and maintain production-quality code, leveraging modern AI coding assistants (e.g., Claude, Cursor) to improve productivity and code quality
• Proficiency in SQL
• Clear written and verbal communication - able to explain statistical reasoning to non-technical stakeholders
• Ability to operate autonomously and influence decisions across teams without direct authority.

Nice to have:

• Experience with probabilistic programming frameworks (e.g. PyMC or Numpyro)
• Familiarity with MLOps tooling (experiment tracking, model serving, monitoring)
• Familiarity with approximate inference methods (variational inference, MCMC)
• Experience with PySpark
• Experience in the Mobile Gaming industry

Subject to applicable laws, we may use artificial intelligence (AI) tools to assist our recruitment teams in the hiring process, including drafting job descriptions, communication, response to applications, assessments and tests, as further described in our Candidates Privacy Notice. By applying to this job, you acknowledge that you have read and understood our Candidates Privacy Notice, including with respect to the use of AI tools, and consent to the processing of your information as described therein. We are an equal opportunity employer and value diversity at our company. We do not discriminate on the basis of race, religion, color, national origin, gender, sexual orientation, age, marital status, veteran status, or disability status.