Senior Data Scientist / Senior Machine Learning Scientist

hackajob is collaborating with Just Eat to connect them with exceptional professionals for this role. Ready for a challenge? Then Just Eat Takeaway.com might be the place for you. We’re a leading global online delivery platform, and our vision is to empower everyday convenience. Whether it’s a Friday-night feast, a post-gym poke bowl, or grabbing some groceries, our tech platform connects tens of millions of customers with hundreds of thousands of restaurant, grocery and convenience partners across the globe.

About this role

The AI Growth team builds the AI systems that make JET's marketplace more relevant for millions of customers and partners across 14 countries. We develop JET's foundation model platform, train and serve embedding models for search and recommendations, and build the intelligent targeting systems that power personalised offers and push notifications. As a Senior Data Scientist, you will own complex, multi-component ML solutions from problem framing through to production measurement. You will be the technical lead on your workstream — making and defending modelling decisions, designing evaluation frameworks, and shaping how the team approaches new problem classes. Working closely with ML Engineers and Data Engineers, your models will reach meaningful commercial scale and impact millions of customer journeys daily.

Key responsibilities

• Own end-to-end ML projects from problem framing through to production deployment, defining approaches, managing trade-offs, and communicating findings to stakeholders.
• Produce technical design documents that guide modelling choices, weighing data availability, serving latency, interpretability, and long-term maintainability.
• Design and own LLM-based solutions for customer or partner representations, content personalisation, or recommendation, including training data curation and evaluation methodology.
• Build evaluation frameworks that link to business metrics, run well-powered online experiments, and investigate offline-to-online performance gaps.
• Close the gap between offline model performance and online business impact through rigorous experimentation and measurement.
• Act as primary technical reviewer for junior colleagues, providing substantive, teaching-oriented feedback that raises the team's overall standard.
• Collaborate with ML Engineers and Data Engineers to ensure models reach meaningful commercial scale across multiple markets.
• Shape technical direction across the AI stack, spanning search ranking, homepage personalisation, promotions intelligence, and foundation model applications.

What will you bring to the team?

• Several years of hands-on data science experience owning ML systems end-to-end in production environments.
• Production-quality Python skills and confident SQL for working with large-scale data warehouses.
• Experience building offline evaluation frameworks from scratch, including metric selection, holdout strategy, leakage checks, and documented links to business metrics.
• Practical experience designing data pipelines for production models, including feature specification, lookback window rationale, and handling sparse data and cold-start cases.
• Hands-on experience with retrieval, ranking, or embedding-based approaches in recommendation or personalisation contexts.
• Experience building evaluation frameworks for LLM-based outputs, including quality dimensions, judge pipelines, and hallucination checks.
• Confidence with A/B test design at scale, including randomisation unit selection, statistical power calculations, and accounting for novelty effects.
• Strong written and verbal communication skills, able to translate complex modelling decisions into clear recommendations for technical and non-technical audiences.
• An analytical problem-solving mindset, comfortable with ambiguity and able to bring clarity to complex questions.

Bonus skills:

• Familiarity with causal inference or uplift modelling in e-commerce or marketplace contexts.
• Parameter-efficient fine-tuning of large language models.
• Experience with ML orchestration or experiment tracking tooling.

At JET, this is how we play. Our teams forge connections internally and work with some of the best-known brands on the planet, giving us truly international impact in a dynamic environment. Being the best at what we do isn’t just about delivering on our strategy. It's a competition for something incredibly valuable – our customers' choice. Every time a customer decides where to order, they're picking a side. At the heart of the JET Customer League are our values and behaviours. They guide every interaction, every decision, every innovation. These are the actions we need to perform consistently and brilliantly, to surpass the competition and earn our customers’ loyalty, again and again. Fun, fast-paced and supportive, the JET culture is about movement, growth, helping one another to succeed and celebrating wins. By truly living our values and embodying our behaviours, we’re building a customer-first culture which enables us to stay one step ahead of the competition.

Inclusion, Diversity & Belonging

No matter who you are, what you look like, who you love, or where you are from, you can find your place at Just Eat Takeaway.com. We’re committed to creating an inclusive culture, encouraging diversity of people and thinking, in which all employees feel they truly belong and can bring their most colourful selves to work every day.

Are you ready to join the team? Apply now!