Senior Data Scientist (AdTech)

Location: Europe, Albania, Poland, Romania, or Ukraine

Company

hirify.global provides software engineering and data science services, including machine learning solutions for large-scale production systems.

What you will do

• Build censored bid-landscape and real-time win-probability models for live advertising auctions.
• Develop conversion propensity, look-alike audience, hierarchical lift estimation, and advertiser-level calibration models.
• Design offline evaluation frameworks using inverse-propensity scoring, doubly robust estimators, and importance reweighting.
• Implement exploration, propensity logging, and constrained optimization strategies for campaign objectives, pricing, and volume targeting.
• Contribute to data diagnostics, model recommendations, scalable ML platform architecture, and post-launch validation.
• Prepare technical documentation and knowledge-transfer materials for the customer’s internal data science team.

Requirements

• 5+ years of experience in machine learning or data science with production-grade models measured against business KPIs.
• Expert Python, machine learning, SQL, and gradient-boosting skills with XGBoost, LightGBM, or CatBoost.
• Strong experience with NumPy, pandas, scikit-learn, large-scale datasets, Spark or PySpark, and structured or behavioral feature engineering.
• Knowledge of probability, statistics, regularization, calibration, categorical feature handling, experimentation, A/B testing, and advanced model validation.
• Experience with temporal splits, leakage detection, drift analysis, slice-based metrics, SHAP, and permutation importance.
• Upper-Intermediate English level or higher and availability in the listed European locations are required.

Nice to have

• AdTech experience with CTR/CVR prediction, bid-landscape modeling, audience segmentation, or RTB mechanics.
• Experience with sparse, delayed, or censored labels, attribution modeling, survival analysis, or positive-unlabeled learning.
• Knowledge of counterfactual evaluation, causal inference, uplift modeling, constrained optimization, or managed ML environments such as Vertex AI.
• Publications, competitive modeling achievements, or open-source contributions related to machine learning or AdTech.

Culture & Benefits

• Work on technically challenging products and large-scale production systems.
• Collaborate with experienced engineers, data scientists, and a customer-side data science organization.
• Operate in a highly data-driven environment with emphasis on scientific rigor and evidence-based decisions.
• Participate in architecture discussions and scalable ML platform design.