Lead Machine Learning Engineer, Chat in London

Machine Learning Engineers at Cleo work on building novel solutions to real-world problems. This work may involve creating chatbots to coach users around their financial health, building classifiers to better understand transaction data, or optimizing transactions within our payments platform. They train, deploy, and improve machine learning models in production, ensuring they deliver meaningful impact for our users.

We’re looking for our next Lead Machine Learning Engineer to join our Chat Evaluations team. You’ll shape and guide technical work within a team of adaptable, creative and product-focused engineers, who deliver ML/AI features that improve the observability of chatbot quality and power the AI development cycle.

Here are some examples, big and small, of the kinds of product feature work our ML Engineers have taken part in over the last year:

• Deployed best-in-class credit decisioning models which affect millions of customers, using open banking data rather than traditional credit scoring.
• Developed models to interpret transactional data, enhancing the understanding of users’ finances.
• Fed user interaction data into fine-tuned LLMs and contextual ranking models, so Cleo knows how to start and continue an engaging conversation.
• Developed optimisation models to improve payment success rates for customers while minimising business costs, tackling this as a two-sided optimisation challenge.
• Designed and implemented AI agents to analyse and extract insights from users’ transactional data.

Experience deploying multiple machine learning models into production.

5+ years of experience in data science, machine learning engineering, or related roles.

Experience integrating and evaluating LLMs.

Excellent knowledge of both Data Science (Python, SQL) and production tools.

Understanding of probability and statistics fundamentals.

Strong ability to communicate findings to non-technical stakeholders.

Experience of leading projects involving multiple people including developing a short term roadmap and reporting progress.

Comfortable breaking down work incrementally.

Nice to have:

• Familiarity with Docker containers and container orchestration tools.
• Experience with LLM-as-a-judge and/or annotation pipelines.

What do you get for all your hard work?

• A competitive compensation package (base + equity) with 3-yearly reviews, aligned to our termly OKR planning cycles. The salary bandings for this role are: £116,510 - £144,319 London, Hybrid / £111,296 - £139,273 UK, Remote.
• Work at one of the fastest-growing tech startups, backed by top VC firms, Balderton & EQT Ventures.
• A clear progression plan. We want you to keep growing. That means trying new things, leading others, challenging the status quo and owning your impact. Always with our complete support.
• Flexibility. We can’t fight for the world’s financial health if we’re not healthy ourselves. We work with everyone to make sure they have the balance they need to do their best work.
• Work where you work best. We’re a globally distributed team. If you live in London we have a hybrid approach, we’d love you to spend one day a week or more in our beautiful office. If you’re outside of London, we’ll encourage you to spend a couple of days with us a few times per year. And we’ll cover your travel costs, naturally.

Other benefits:

• Company-wide performance reviews every 4 months.
• Generous pay increases for high-performing team members.
• Equity top-ups for team members getting promoted.
• 25 days annual leave a year + public holidays (+ an additional day for every year you spend at Cleo, up to 30 days).
• 6% employer-matched pension in the UK.
• Private Medical Insurance via Vitality, dental cover, and life assurance.
• Enhanced parental leave.
• 1 month paid sabbatical after 4 years at Cleo.
• Regular socials and activities, online and in-person.
• We'll pay for your OpenAI subscription.
• Online mental health support via Spill.
• Workplace Nursery Scheme.
• And many more!

Welcoming Everyone: We strongly encourage applications from people of colour, the LGBTQ+ community, people with disabilities, neurodivergent people, parents, carers, and people from lower socio-economic backgrounds. If there’s anything we can do to accommodate your specific situation, please let us know.