Senior Polyglot Engineer – Build Impactful Fintech in London

About Cleo

At Cleo, we're not just building another fintech app. We're embarking on a mission to fundamentally change humanity's relationship with money. Imagine a world where everyone, regardless of background or income, has access to a hyper-intelligent financial advisor in their pocket. That's the future we're creating. Cleo is a rare success story: a profitable, fast-growing unicorn with over $300 million in ARR and growing over 2x year-over-year. This isn't just a job; it's a chance to join a team of brilliant, driven individuals who are passionate about making a real difference. We have an exceptionally high bar for talent, seeking individuals who are not only at the top of their field but also embody our culture of collaboration and positive impact.

If you’re driven by complex challenges that push your expertise, the chance to shape something truly transformative, and the potential to share in Cleo’s success as we scale, while growing alongside a company that’s scaling fast, this might be your perfect fit.

About the role

At Cleo, we care far more about how you think than which language you’ve used before. While much of our product runs on Ruby today, we’re deliberately hiring polyglot engineers because diverse technical backgrounds make our teams stronger — different languages shape how you solve problems, reason about systems, and design clean software. If you’ve shipped meaningful product work in any modern stack, you’ll ramp quickly here. What matters most is curiosity, thoughtful engineering, and a willingness to learn, not a perfect match on our tech.

What you'll be doing

• You’ll join a cross-functional product squad and work closely with engineers, designers, analysts, and product partners to build features that improve our users’ financial health.
• You’ll shape the direction of upcoming work, break down problems with your team, and help drive projects from early discovery all the way to shipped impact.
• Day‑to‑day, you’ll work across our backend and product systems – much of which runs in Ruby today – but you don’t need Ruby experience to thrive here.
• You’ll build and evolve APIs, data models, and business logic; contribute to testing, observability, and experimentation; and help us continuously improve developer experience and product quality.
• You’ll mentor others at your level (mid, senior, or beyond), share knowledge generously, and contribute to a team culture where engineers grow quickly and have real influence.

A few examples of the work our engineers shipped recently:

• Building a secured credit card
• Launching new budgeting and financial insight features
• Running subscription and pricing experiments

About you

You care about building products that genuinely help people, and improving financial health is a mission that resonates with you. You’re an engineer with solid fundamentals who has worked in any modern tech stack – the exact language isn’t important. What matters is your ability to reason clearly, learn quickly, think in trade‑offs, and write maintainable, thoughtful code.

You collaborate well with product, design, and data; you’re curious about users; and you enjoy shaping work beyond just the technical bits. Whether you’re mid‑level, senior, or leading teams already, you contribute positively to engineering culture, support others, and help raise the bar for those around you.

You align with our values and engineering principles – rooted in autonomy, accountability, pragmatism, and building things that genuinely improve people’s lives.

Our tech stack

Cleo is built as a Ruby on Rails monolith with a single React Native app frontend, utilising TypeScript. We also leverage Python for machine learning services and PostgreSQL for our database, all hosted on AWS. Our CI/CD pipeline is fully automated, with production deployments happening on every merge via Kubernetes. Our backend engineers deploy multiple times a week, and we release our frontend app to Google and Apple for review at least once a week.

While we take a pragmatic approach, we place a strong emphasis on quality. Our code is peer‑reviewed, and we maintain automated testing using Minitest and CircleCI. We're also actively working towards a more modular architecture, focusing on separating concerns to achieve all the benefits of microservices within a monolith, while progressively refactoring our code as we build new features. Everyone in the engineering team contributes to driving our technical strategy, voices & ideas from all levels are valued: we are all owners at Cleo.

What do you get for all of your hard work?

• A competitive compensation package (base + equity) with three annual reviews, aligned to our termly OKR planning cycles.
• 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 6 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!

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.

UK App access: The Cleo app is no longer downloadable in the UK (but only until next year). If you’re an existing user, you’ll still have access to the app. But some features won’t be available (just for a little while). Why? 99% of our users are based in the US – where financial health is often overlooked. We’ve decided to shift our focus to where we can provide the most value and make the greatest impact for users who need it most. Then we’ll be able to apply what we learn to better support our UK users in the future.