Mid-Senior Backend Engineer (ML integrations)

About Cleo

At Cleo were not just building another fintech app. Were embarking on a mission to fundamentally change humanitys relationship with money. Imagine a world where everyone regardless of background or income has access to a hyperintelligent financial advisor in their pocket. Thats the future were creating.

Cleo is a rare success story: a profitable fastgrowing unicorn with over $200 million in ARR and growing over 2x yearoveryear. This isnt just a job; its 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 youre driven by complex challenges that push your expertise the chance to shape something truly transformative and the potential to share in Cleos success as we scale while growing alongside a company thats scaling fast this might be your perfect fit.

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About the Role

Youll join the team responsible for building and maintaining the decisioning systems that power Cleos core product. This is one of the most businesscritical domains at Cleo and one of our most impactful directly driving user experience growth and profitability.

Your primary focus will be integrating MLdriven credit and eligibility models into our Ruby on Rails monolith. These models written in Python by ML engineers and data scientists require robust scalable integration patterns; youll own the productionisation of those services: from data ingestion and interface design to monitoring alerting and runtime observability.

Youll work closely with ML engineers analysts and PMs to expose model outputs cleanly help debug behavioral anomalies and ensure that stakeholders have the tooling they need to understand how decisions are made.

Youll also be part of our wider Ruby chapter working across our Ruby monolith to improve it for both our users as well as your fellow engineers.

What Were Looking For

Youre a backend engineer whos comfortable working in technically complex domains particularly those involving machine learning financial decisioning or largescale data systems.

Youre proficient in Ruby and have experience building and maintaining production systems that interface with machine learning models data pipelines or highthroughput decision engines. Exposure to Python and ML concepts is a plus but deep ML knowledge isnt required.

You care about observability system reliability and deployment best practices. You know how to make integrations robust and maintainable and how to ensure they operate correctly in production over time.

Youre dataaware able to reason about data lifecycle ownership transformations and how downstream consumers rely on it. Youre also a strong crossfunctional collaborator able to work closely with product managers analysts and ML engineers to debug issues and iterate quickly.

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 Heroku. 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 peerreviewed and we maintain automated testing using Minitest and CircleCI. Were 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 your hard work

• A competitive compensation package (base equity) with biannual reviews aligned to our quarterly OKR planning cycles. You can view our public progression framework and salary bandings here: at one of the fastestgrowing 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 cant fight for the worlds financial health if were 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. Were a globally distributed team. If you live in London we have a hybrid approach wed love you to spend one day a week or more in our beautiful office. If youre outside of London well encourage you to spend a couple of days with us a few times per year. And well cover your travel costs naturally.
• Other benefits;
• Companywide performance reviews every 6 months
• Generous pay increases for highperforming team members
• Equity topups 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% employermatched 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 inperson
• Well 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 socioeconomic backgrounds.

If theres 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 youre an existing user youll still have access to the app. But some features wont be available (just for a little while). Why 99% of our users are based in the US where financial health is often overlooked. Weve 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 well be able to apply what we learn to better support our UK users in the future.