Senior Data Scientist - Technical Specialist in London

In Customer Data Science (part of the Data Science Hub), we build the systems behind personalised customer decisioning – from customer segmentations to offer optimisation. We impact millions of customers, bringing them value and earning their loyalty.

This team personalises all of the offers you see in the Nectar app, and we aim to personalise everything that matters – offers, online recommendations, digital experiences, communications. We achieve this using our incredible data asset, our rich customer understanding, and state of the art machine learning and AI.

This is a new and unique role. You’ll operate as a deep technical specialist, floating across two teams in Customer Data Science. You’re not here to manage a team; you’re here to solve the hardest problems, raise the technical bar, and ensure that we are building robust, production-grade products.

This isn’t a consultancy role – you’ll drop into ambiguous, high-impact problems, and solve them yourself. But you’ll also define the patterns we need – how we build models, how we productionise them, how we scale without breaking.

What you’ll do

• Solve the hard problems: Take on ambiguous, high-value problems across customer understanding, personalisation, optimisation and decisioning.
• Advance techniques used across the team (uplift modelling, optimisation, causal inference, recommendations, real-time decisioning).
• Define and embed best practice across modelling, experimentation, deployment, and model lifecycle management.
• Drive consistency in how we structure codebases, version control, testing and reproducibility.
• Coach through doing – pairing on code, demonstrating standards, piloting your ideas.
• Represent our needs to the Platform team, ensuring we get the ML Ops platform we need.
• Work with the ML Engineering team to shape how we architect our end-to-end solution.
• Become the recognised data science technical expert in Customer Data Science, bringing new ideas for future approaches.
• Understand how our business really works, including by supporting our stores during peak trading periods.
• Actively contribute to our vibrant Data and Analytics community of over 800 colleagues.

Who you are

We’re looking for a highly motivated self-starter – technical lead who fixes problems and creates value without micromanagement. You need to thrive in an ambiguous role, and know how to balance our need for technical rigour against our need to deliver commercial and customer value.

Value delivery

• Deep experience in Data Science roles, with evidence of solving complex problems end-to-end.
• A record of building personalisation systems which run in production, and an understanding of the value these generated.
• Experience working in an Agile way, and ability to understand the trade-off between immediate value, future value, and technical rigour.
• A strong ability to communicate ideas to audiences of varying technical background and seniority.

Data Science expertise

• Strong grounding in statistical modelling and machine learning, such as predictive modelling at scale, unsupervised learning, causal inference, experimentation, optimisation and decisioning.
• Strong understanding of the “how” behind the algorithm; ability to select the right technique for a given objective and avoid pitfalls.
• Curiosity, scepticism and attention to detail regarding data quality, samples, bias and ethics.

Production-grade design

• Extensive programming ability across Python and strong ability to use SQL, with proven experience of developing complex solutions in a corporate environment.
• Solid understanding of version control, dependency management, CI/CD and automated testing, and batch and near real-time processing.
• Practical experience working on cloud-based ML Ops platforms.
• Ability to see the big picture – from data ingestion to decisioning output.

Development and coaching

• A strong awareness and understanding of technology trends and direction in Data Science, analytics and AI.
• Ability to support in the development, training and mentoring of others.

Essential Criteria

• Extensive Data Science background.
• A record of building systems which run in production.
• A strong ability to communicate ideas to audiences of varying technical background and seniority.
• Strong grounding in statistical modelling and machine learning, including predictive modelling and recommendations/decisioning.
• Extensive programming ability across Python and strong ability to use SQL.
• Solid understanding of working with production codebases, such as version control, CI/CD, batch and real time processing.
• Strong understanding of ML Ops and working in cloud environment.

We are committed to being a truly inclusive retailer so you’ll be welcomed whoever you are and wherever you work. Around here, there’s always the chance to try something new — whether that’s as part of an evolving team or somewhere else across the business - and we take development seriously and promise to support you. We also recognise and celebrate colleagues when they go the extra mile and, where possible, offer flexible working. When you join our team, we’ll also offer you an amazing range of benefits.

Starting off with colleague discount, you'll be able to save 10% on your shopping online and instore at Sainsbury's, Argos, TU and Habitat, and we regularly increase the discount to 15% at points during the year. We've also got you covered for your future with our pensions scheme and life cover. You'll also be able to share in our success as you may be eligible for a performance-related bonus of up to 20% of salary, depending on how we perform.

Your wellbeing is important to us too. You'll receive an annual holiday allowance, and you can buy up to an additional week's holiday, and we provide private healthcare. We also offer other benefits that will help your money go further such as season ticket loans, interest free car loan of up to 10k, cycle to work scheme, health cash plans, salary advance (where you can access some of your pay before pay day) as well access to a great range of discounts from hundreds of other retailers. And if you ever need it there is also an Employee Assistance Programme.

Moments that matter are as important to us as they are to you which is why we give up to 26 weeks’ pay for maternity or adoption leave and up to 4 weeks’ pay for paternity leave.

At Sainsbury’s, data sits at the heart of how we operate, innovate and serve our customers. Our Data & Analytics team is building a technically advanced, commercially focused and impactful capability, powering our Next Level Strategy and helping to create a Sainsbury’s powered by industry leading AI algorithms. We use data, technology and advanced analytics to drive better decisions across the business, from forecasting and optimisation to experimentation, personalisation and machine learning. With one of the richest retail datasets in the UK and a portfolio spanning Sainsbury’s, Argos, Habitat and Nectar, the opportunity to innovate is huge. Here, you’ll tackle complex challenges at scale, create measurable impact and grow quickly alongside brilliant colleagues. People who thrive with us combine business understanding, technical expertise and curiosity, with a natural instinct for problem-solving. Join us and help shape the future of retail through data and AI.