Data Scientist III

Company at a Glance

OpenX is focused on unleashing the full economic potential of digital media companies. We do this by making digital advertising markets and technologies that are designed to deliver optimal value to publishers and advertisers on every ad served across all screens.
At OpenX , we have built a team that is uniquely experienced in designing and operating high-scale ad marketplaces, and we are constantly on the lookout for thoughtful, creative executors who are as fascinated as we are about finding new ways to apply a blend of market design, technical innovation, operational excellence, and empathetic partner service to the frontiers of digital advertising.
A Data Scientist III is a proficient, fully independent scientist who owns medium-to-large data science projects end-to-end — from problem formulation and research through to deploying and maintaining production models. In this role, you will build production-ready models and analyses that solve real marketplace problems, partner with product and engineering to ship them, mentor junior scientists, and act as a strong technical voice within your team.

Problems at this level include bidding and yield modeling, relevance and prediction systems at exchange scale, experimentation and causal measurement of marketplace changes, and the feature engineering, validation, and monitoring required to run ML reliably in production.

The ideal candidate brings a solid applied machine learning foundation, growing judgment in selecting methods for business problems at scale, and a track record of carrying analytical work from an ambiguous question through to measurable production impact.
What we offer:

- Employment contract (19 550 - 21 850 PLN gross/monthly) OR B2B (160 - 179 PLN net/hourly)

- Working with the newest technologies such as Cloud Computing (GCP)

- Challenges at work that are difficult to find anywhere else!

- Solving important problems in a scale

- Joining a company that is growing and scaling

- Flexible working hours & remote work option

Key Responsibilities:

- Modeling & Technical Execution:

- Own the end-to-end data science lifecycle for moderately complex models and significant project components — spanning data ingestion, feature engineering, modeling, validation, deployment, monitoring, and retraining.

- Apply expertise across several core areas of machine learning and statistics (e.g., gradient-boosted models, deep neural networks, time series, causal inference concepts, experimentation design), selecting appropriate methods for complex data science problems.

- Write efficient, modular, well-tested code for data processing, feature engineering, and model training/inference, leveraging distributed tooling (e.g., Vertex AI pipelines, Dataflow, BigQuery) where appropriate.

- Design and implement robust validation frameworks for complex experiments and models, accounting for potential biases and real-world performance.

- Troubleshoot complex model performance issues, data anomalies, and code bugs effectively with little guidance.

- Execution & Collaboration:

- Define analytical approaches and scope data science projects for moderately complex or ambiguous business problems.

- Partner with product managers and stakeholders to define success metrics and experiment goals, and to translate marketplace problems into data science solutions.

- Lead the design and analysis of experiments (e.g., A/B tests, switchback) for your projects, and interpret complex model results and experimental outcomes with a focus on actionable insights and business outcomes.

- Proactively identify opportunities within your domain where data science can provide significant value, and initiate exploration.

- Follow and help improve established team processes for coding standards, documentation, reproducibility, and experimentation.

- Mentorship & Influence:

- Mentor DS I and DS II scientists, providing technical guidance, reviewing code, analyses, and models,