Data Scientist

Our mission is to help large successful brands like Uber, Amazon, Wise, HelloFresh (and more!) put their customers at the centre of everything they do. Using best-in-class tech in a fast-developing AI space, our Customer Experience Intelligence platform continuously analyses explicit and implicit feedback to enable our clients to identify what they should do next.

We're hiring a Data Scientist to join the team and help build and ship the next generation of that stack.

What you'll be doing:

• Train, evaluate, and iterate on ML models for customer feedback tasks, contributing to our custom fine-tuning pipelines and running experiments with rigour and clear documentation.
• Build and maintain LLM-powered features including retrieval pipelines, reranking systems, and insight generation — with support and guidance from senior team members.
• Contribute to evaluation frameworks: help build test sets, define metrics, and assess model quality across classification, extraction, and generative tasks.
• Work on semantic search and retrieval, developing a strong working understanding of embedding-based approaches and the methods that go beyond them.
• Write clean, well-tested code and collaborate with Engineering on model integration, data pipelines, and monitoring.
• Work with the wider Data Science team to translate business and product requirements into practical ML experiments and solutions.
• Stay close to relevant research and bring useful ideas from the literature into team discussions and experiments.

What you’ll need:

• A solid working knowledge of transformer architectures and how they are applied in NLP tasks.
• Proficiency in PyTorch, including training loops and standard model fine-tuning workflows; exposure to parameter-efficient techniques such as LoRA is a plus.
• Experience working with real-world text data across tasks such as classification, extraction, embeddings, or search — at a meaningful scale.
• Some exposure to instruction fine-tuning or model serving, with an interest in going deeper.
• A grounding in classical ML and statistics, and the instinct to reach for simpler methods when warranted.
• Familiarity with GenAI and agentic patterns, even if hands-on production experience is still developing.
• Clear communication skills and the ability to explain technical work to colleagues across functions.
• Genuine curiosity about AI and a habit of experimenting — you learn by doing.
• Good ownership instincts: you follow problems through rather than passing them on.

It would be a bonus if you:

• MSc in Computer Science, Machine Learning, AI, Data Science, Computational Linguistics, or a closely related STEM field.

Our Hiring Process

• Complete an introductory asynchronous interview.
• Have a call with Aji, our Chief Scientist, to learn more about the role.
• Complete a short take home assignment.
• Meet a mix of people from the Data Science, Engineering and Product teams.
• Have a call with our cofounder to learn more about life at Chattermill.

Our Perks

• Flexible working in a choice-first environment.
• Work-from-home allowance to set up your ideal workspace.
• 25 days holiday + local bank holidays, plus an extra day for each year of service.
• Your birthday off.
• Annual learning & development budget to support your growth.
• Equity options — share in the company’s success.
• Monthly health & wellbeing budget, increasing with length of service.
• Optional private healthcare plan.
• Life assurance & income protection (location dependent).
• Employee Assistance Programme (location dependent) for extra support when you need it.
• Enhanced family leave (location dependent), plus fertility and neonatal leave.

Our Values

• We are obsessed with experience.
• We believe in the power of trust.
• We act as responsible owners.
• We share a passion for growth & progress.
• We set our ambitions high but stay humble.
• We believe the right team is the key to success.

Diversity & Inclusion

We want to enable exceptional experiences for everyone, and to achieve this we need everyone’s voice in our team. We are on a mission to bring more diversity into the business and to give everyone (from all backgrounds and abilities) a chance to join us, even if they may not fit all of the requirements set out in this job spec.