Senior Data Scientist, Growth Alliance

HelloFresh; Warszawa; On-site; PLN 240,000 - 360,000; Full time

Benefits offered by this job

Global collaboration

Real-world impact

Leadership

End-to-end delivery

Workspace in Warsaw

Job summary

HelloFresh in Warsaw is seeking a Senior Data Scientist within HelloTech to drive AI-enabled communications. You will design, implement, and scale ML models that personalize messages across channels, leveraging contextual bandits and reinforcement learning to optimize user engagement.

You will collaborate with cross‑functional teams to integrate models into high‑throughput systems, iterate on experimentation designs, and ensure robust performance in production across global markets.

Qualifications

• 5+ years of professional experience in data science, ML, or a related quantitative field.
• Proficient in Python and operating in a modern ML stack (e.g. Databricks/Spark, MLflow) in close collaboration with engineers.
• Strong foundation in machine learning for personalization, plus direct experience with reinforcement learning and/or contextual bandits (e.g. Thompson Sampling, epsilon‑greedy, reward design).
• Solid grounding in experimentation and causal inference — designing and analyzing controlled experiments in high‑traffic settings, and reasoning about guardrails, exposure, and bias.
• Hands‑on with classical ML techniques (regression, classification, clustering, recommendation systems) and comfort choosing the right tool for the problem.
• Experience with customer‑behaviour data, segmentation, and production feature pipelines.
• Clear, structured communication and a genuinely collaborative, cross‑functional mindset.

Responsibilities

• Build, own, and iterate on RL and ML models that run in production behind high‑traffic, performance‑critical conversion and communication flows.
• Develop the decisioning logic that determines the best next action for each user across the funnel and the messaging lifecycle.
• Drive the architectural evolution of our contextual‑bandit systems — from online exploration toward offline policy evaluation and deterministic, low‑latency inference.
• Partner with Engineering on system design so models integrate cleanly into the funnel and messaging architecture.
• Own experimentation design for decisioning models: define success metrics and guardrails, and interpret results in high‑noise, high‑traffic environments.
• Keep models safe and effective in production — monitoring performance, input‑data reliability, drift, and latency, and iterating quickly.
• Collaborate with CRM Ops, Marketing Analytics, and platform partners to turn model behaviour into decisions marketers trust.

Skills

Python

ML stack

Reinforcement learning

Contextual bandits

Experimentation

Causal inference

Classical ML

Customer data

Communication

Tools

Databricks/Spark

MLflow

Job description

Work with HelloFresh in Warsaw and its HelloTech organization, HelloFresh’s global technology backbone with more than 1000 people, building the digital products that power our end-to-end food experience. From meal kits and ready‑to‑eat meals to specialty offerings like pet food and premium meat & seafood, HelloTech creates the platforms that bring tailored food solutions to millions of customers every month.

Our subscription-based, direct-to-consumer model relies on technology at every step, from customer-facing apps and personalization logic to pricing, forecasting, supply chain optimization, and initiatives that help reduce food waste. While our brands operate independently to serve distinct customer needs, they are united by shared platforms, data, and operational excellence built by HelloTech.

HelloTech works in autonomous, cross‑functional alliances, each owning a specific product or domain end to end. By working with our Warsaw office, you will help shape scalable, data‑driven products used across our markets, working with a modern tech stack and international teams to continuously improve how people discover, order, and enjoy HelloFresh’s products, today and in the future.

About the role: What’s in the Box

The Communications tribe, a key part of the Growth Alliance, enables our brands to deliver highly personalized, meaningful interactions with our users across global markets. As a Senior Data Scientist within this team, you will drive a direct business impact by shaping the intelligence behind how, when, and what we communicate with our customers.

Your Work Will Primarily Focus On Three Core Initiatives

• Send Decisioning: Designing and scaling AI agents, specifically using contextual bandits, to optimize our communication channels (email, SMS, and push notifications). Your models will automate the logic that determines the most relevant message and timing for each individual user.
• Intelligent Funnel: Supporting a collaborative, cross‑tribe initiative aimed at personalizing the post‑click experience. You will leverage contextual bandits to match user ad‑context and pre‑questionnaire preferences with the optimal landing page journey.
• AI‑Assisted Content & Search: Building intelligent systems to index and search internal marketing assets (images and copy). Additionally, you will develop tools that assist marketing teams in the automated composition of new, high‑performing communication assets.

To succeed in this project, you should be a pragmatic and curious problem solver who excels in a cross‑functional environment. Success involves translating complex user behavior into scalable models, identifying opportunities to improve our data foundations, and balancing technical depth with a strong focus on driving user engagement.

At HelloTech, flexibility and cross‑functional collaboration are core to how we work. While this role is aligned to a specific Alliance, strong candidates may also be considered for opportunities across different teams or projects.

What you’ll do: The Recipe

• Build, own, and iterate on RL and ML models that run in production behind high‑traffic, performance‑critical conversion and communication flows.
• Develop the decisioning logic that determines the best next action for each user across the funnel and the messaging lifecycle.
• Drive the architectural evolution of our contextual‑bandit systems — from online exploration (Bootstrapped Thompson Sampling) toward offline policy evaluation and deterministic, low‑latency inference (Counterfactual Risk Minimization, Offset Trees, model distillation).
• Partner with Engineering on system design so models integrate cleanly into the funnel and messaging architecture — including where models decide, how decisions are served at latency, and how failures are handled and rolled back.
• Own experimentation design for decisioning models: define success metrics and guardrails, and interpret results in high‑noise, high‑traffic environments using rigorous methods (sequential testing / SPRT, propensity handling, allocation‑bias‑free setups).
• Keep models safe and effective in production — monitoring performance, input‑data reliability, drift, and latency, and iterating quickly when issues surface.
• Collaborate with CRM Ops agent leads, Marketing Analytics, and platform partners to turn model behaviour into decisions marketers trust.

What you’ll bring: The Ingredients

• 5+ years of professional experience in data science, ML, or a related quantitative field, with a track record of shipping models to production.
• Proficient in Python and experienced operating in a modern ML stack (e.g. Databricks/Spark, MLflow) in close collaboration with engineers.
• Strong foundation in machine learning for personalization, plus direct experience with reinforcement learning and/or contextual bandits (e.g. Thompson Sampling, epsilon‑greedy, reward design).
• Solid grounding in experimentation and causal inference — designing and analyzing controlled experiments in high‑traffic settings, and reasoning about guardrails, exposure, and bias.
• Hands‑on with classical ML techniques (regression, classification, clustering, recommendation systems) and comfort choosing the right tool for the problem.
• Experience with customer‑behaviour data, segmentation, and production feature pipelines.
• Clear, structured communication and a genuinely collaborative, cross‑functional mindset.

Nice To Have

• Off‑policy evaluation/counterfactual learning, propensity methods, or sequential testing (SPRT).
• Experience with experimentation platforms (e.g. Statsig) and streaming/low‑latency inference.
• Working with unstructured data as model features (embeddings, text signals).
• Exposure to marketing/CRM decisioning, deliverability, or funnel/conversion optimisation.

Above all, we are looking for individuals who will make HelloFresh better. We believe there are many different ways of developing skills and we love diverse experiences! So even if you don’t “tick all the boxes” but think you’d thrive in this role, we would really like to learn more about you.

What we offer: The Toppings

• Global collaboration at scale: Collaborate with experienced engineers and product partners across HelloTech’s international teams, in a culture of active knowledge sharing.
• Technology with real‑world impact: Build and operate modern systems at global scale, supporting 6+ millions of customers and complex supply chain operations.
• Technical/Product/Design leadership: Drive best practices and influence architecture/design, quality, and ways of working in an autonomous, product‑led setup.
• End‑to‑end development/delivery: Drive decisions from problem definition to production, improving systems and enabling long‑term scalability.
• Access to workspace at Warsaw Centre Point. The hub offers modern facilities including showers, breakout zones, outdoor space, cycle parking, and refreshments (coffee, soft drinks, and fruit).

Are you the missing ingredient? If this sounds like a tasty opportunity, we’d be excited to hear from you. We aim to review your profile and respond within 5 business days.