Senior Data Scientist, Growth Alliance

HelloFresh's HelloTech organisation, based in Warsaw, powers digital products for meal kits, ready-to-eat meals, and specialty food offerings for millions of customers. HelloTech creates shared platforms used across multiple brands leveraging technology for customer-facing apps, personalization, pricing, forecasting, and supply chain optimization.

• 5+ years of experience in data science, ML, or related quantitative fields with a track record of shipping production models.
• Proficient in Python and experienced with modern ML stacks such as Databricks, Spark, and MLflow.
• Strong foundation in machine learning personalization techniques with direct experience in reinforcement learning and contextual bandits (e.g., Thompson Sampling, epsilon-greedy).
• Solid grounding in experimentation and causal inference, including designing and analyzing controlled experiments in high-traffic environments.
• Experience with classical ML techniques like regression, classification, clustering, and recommendation systems.
• Experience handling customer-behavior data, segmentation, and production feature pipelines.
• Clear and structured communication skills with a collaborative, cross-functional mindset.

Nice to have:

• Experience with off-policy evaluation, counterfactual learning, propensity methods, or sequential testing (SPRT).
• Familiarity with experimentation platforms such as Statsig and streaming or low-latency inference.
• Experience working with unstructured data including embeddings and text signals.
• Exposure to marketing/CRM decisioning, deliverability, or funnel and conversion optimization.

• Build, own, and iterate on reinforcement learning (RL) and machine learning (ML) models in production for conversion and communication flows.
• Develop decisioning logic for best next actions across user funnels and messaging lifecycle.
• Drive architectural evolution of contextual-bandit systems including online exploration and offline policy evaluation.
• Partner with engineering on system design to integrate models with funnel and messaging architecture, handling latency and failure.
• Own experimentation design and interpret results using rigorous statistical methods like sequential testing (SPRT).
• Monitor and maintain model safety, performance, input-data reliability, drift, and latency in production.
• Collaborate with CRM operations, marketing analytics, and platform partners to build trust in model decisions.