Principal Machine Learning Engineer - Personalisation United Kingdom

United Kingdom

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.

About Cleo

Most people come to Cleo to do work that matters. Every day, we empower people to build a life beyond their next paycheck, building a beloved AI that enables you to forge your own path toward financial well-being.

Backed by Tier 1 investors, we’ve reached millions of people to support them throughout their financial lives, from their first paycheck to their first home and beyond. We’re hitting headlines too. This year, Forbes named us as one of their Next Billion Dollar Startups, and we were crowned the ‘Hottest Tech Scaleup’ at the Europas.

Machine Learning Engineers at Cleo work on building novel solutions to real-world problems. This really does vary but could be: creating chatbots to coach our users around their financial health, creating classifiers to better understand transaction data or even optimising transactions within our payments platform.

Ultimately, we’re looking for a brilliant Principal Machine Learning Engineer to join us on our mission to fight for the world’s financial health. You’ll be leading technical work within a team of adaptable, creative and product-focused engineers, who train & integrate cutting edge machine learning across a variety of products and deploy them into production for millions of users. We understand our customers, we understand their pain, and we are passionate about helping them.

What you’ll be doing

• Training and fine-tuning models to help customers get more value from our chatbot and app through deeper personalisation, creating a smarter & more engaging experience.
• Integrating our models with LLMs hosted by OpenAI, Anthropic, GCP, AWS.
• Working cross-functionally with backend engineers, data analysts, UX writers, product managers, and others to ship features that improve our users’ financial health.
• Driving the adoption of appropriate state-of-the-art techniques for recommendation, message campaign optimisation, and contextual bandits.
• Communicating the team’s successes and learnings at the company level & beyond.
• Developing a holistic view of personalisation and user-level features across Cleo, taking the initiative to extend existing approaches to benefit new areas of the app and conversations.
• Supporting ML Engineers around problem framing, ML modelling, and evaluation.

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:

• Designed and implemented AI agents to analyse and extract insights from users’ transactional data.
• Developed models to interpret transactional data, enhancing the understanding of users’ finances.
• Created contextual intent classifiers to understand user conversations with Cleo, enabling tailored and accurate platform responses.
• Engineered ML models to identify and deliver relevant actions to users within Cleo, ensuring a seamless, context-aware conversational experience.
• Built models to evaluate risk in customer interactions with bank transaction features and user activities.
• Developed optimisation models to improve payment success rates for customers while minimising business costs.

Whatever problem you tackle, and whichever team you join, your work will directly impact those most in need, helping to improve their financial health.

What you’ll need

• Experience in industry machine learning roles as a technical leader or principal/staff engineer.
• Excellent knowledge of both Data Science (python, SQL) and production tools.
• A deep understanding of probability and statistics fundamentals.
• Big picture thinking to correctly diagnose problems and productionising research.
• Top tier communication skills, to be able to partner with Product and Commercial Leaders.
• Industry-leading contributions to your field, communicated through conferences, blogs, talks, or open-source projects.

Nice to have

• Strong experience with additional programming languages, such as Java, Scala, C++.
• Broader contributions to your field through: conferences, blogs, talks, or open-source projects.

What do you get for all your hard work?

• A competitive compensation package (base + equity) with bi-annual reviews. You can view our public progression framework and salary bandings here: – This position is a DS5 level and we can pay £111,184 – £145,088 p.a depending on experience.
• 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 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; if you’re outside of London, we’ll encourage you to spend a couple of days with us a few times per year.
• Other benefits:
• 25 days annual leave a year + public holidays (+ an additional day for every year you spend at Cleo).
• 401k matching in the US and 6% employer-matched pension in the UK.
• Private Medical Insurance.
• 1 month paid sabbatical after 4 years at Cleo!
• Online courses & internal training to level up your skills.
• Regular socials and activities, online and in-person.
• Online mental health support via Spill.
• And many more!

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