Principal Data Scientist

We’re building a huge technology company that makes it easier to move between countries. To drive exponential growth, we need a team of extremely ambitious people.

We’re on a mission to make migration easy

We started building Marshmallow in 2017. Since then, we’ve grown from 3 to 700+ people, gained unicorn status, raised ~£140M over three funding rounds, turned profitable, insured millions of drivers and lent millions in car loans.

But we’re only just getting started. Our goal is to become one of the largest financial services providers in the world. Over the next 10 years we’ll grow exponentially, not only by scaling our existing products, but also by building new ones.

To achieve our goals we need incredibly ambitious, commercially driven people who never settle for ‘good enough’. Marshmallowers are hungry for autonomy and ownership, and would rather improve than coast. Everyone raises standards and has an impact, with a focus on collective success over self-interest.

We’ve created an environment where curious, tenacious people win and grow together. If that sounds motivating, this could be the place for you.

Our values

Our values aren’t words on a wall. They define how we show up - how we think, challenge ideas, and continue to raise the bar.

Explore our open roles to see where you could make an impact.

This is a place for do-ers. We take ownership of meaningful problems and move them forward, even when the context is ambiguous or the path isn’t fully defined.

We relentlessly improve

Progress here is deliberate. We don’t settle. We question assumptions, seek honest feedback, and refine how we work to achieve better outcomes.

We have low ego

Hierarchy doesn’t matter here - ideas do. We welcome challenge, prioritise what’s right over who’s right, and hold ourselves accountable for the decisions we make.

Why Marshmallow?

Accelerate your career with us

1

Supercharged growth

2

High-performing people

You’ll join a group of smart, highly driven people who leave egos at the door. We’re collaborative and curious, and hold ourselves, and each other, to incredibly high standards.

Our teams spend a lot of time together in person to drive collective ideation, quality feedback conversations, and faster decision-making. Our offices have been designed with collaboration at the core, along with spaces to come together as a community.

3

Autonomy and ownership

Every team has a clear north star goal and the autonomy to influence roadmaps, steering the best approach to solve problems. That autonomy extends to individuals too - we expect everyone to take ownership, experiment and share ideas to drive better outcomes.

Hear from the people raising the bar every day

Gergo

"The gap between having an idea and acting on it is genuinely small here. You're expected to move fast, bring your own urgency, and not wait for permission. The people around you operate the same way: high-energy, high-integrity, and never settling for good enough. Being surrounded by that every day raises your own standards and keeps raising them."

Bia

“Innovation is at the core of everything we do. We ringfence time every week to experiment and explore, protected from day-to-day delivery. If we discover an opportunity to drive better outcomes, we have the autonomy to act on it. Increasingly, the most valuable discoveries are happening through AI. AI is a strategic priority and our commitment to it is only accelerating. The people who thrive here don't just lean into new initiatives. They actively drive them.”

Vik

Group Product Manager

"Most companies wait to have all of the information in place before acting. We don't. When AI started changing the landscape, we rolled up our sleeves and started building straight away - because growth here is practical, not theoretical. You're expected to take real ownership and move fast. When something isn't working, we challenge our thinking and pivot. Responding to the data and staying agile matters far more than being right the first time."

Learn how we work in London and Budapest

If you don’t see anything that fits you today, check back soon. We’re scaling quickly, putting up new roles every week.

Principal Data Scientist

Location

London

Employment Type

Full time

Location Type

Hybrid

Department

Data Data Science

We’re on a mission to make migration easy.

We started building Marshmallow in 2017. Since then, we’ve grown from 3 to 700+ people, gained unicorn status, raised ~£140M over three funding rounds, turned profitable, insured millions of drivers and lent millions in car loans.

But we’re only just getting started. Our goal is to become one of the largest financial services providers in the world. Over the next 10 years we’ll grow exponentially, not only by scaling our existing products, but also by building new ones.

To achieve our goals we need incredibly ambitious, commercially driven people who never settle for ‘good enough’. Marshmallowers are hungry for autonomy and ownership, and would rather improve than coast. Everyone raises standards and has an impact, with a focus on collective success over self-interest.

We’ve created an environment where curious, tenacious people win and grow together. If that sounds motivating, this could be the place for you.

London (hybrid, 3 days in office)

Data Science at Marshmallow

Our Data Science team partners across the business to turn data into better decisions, smarter products, and simpler customer journeys. We work closely with Product, Engineering, and Operations to build and ship models and AI systems that are reliable in production and deliver measurable impact.

Within Data Science, this role sits in Claims, supporting the function and the broader ambition to automate more of the claims journey. Claims is one of Marshmallow's most important customer touchpoints, and we're looking for a Principal Data Scientist who can provide technical leadership across traditional ML and Generative AI, bring system-level thinking to how we scale decisioning, and confidently challenge proposals to ensure we build robust, sustainable solutions.

What you'll be doing

Provide technical leadership for data science across Claims Fraud, shaping the approach to risk decisioning and fraud detection in partnership with Product and Engineering

Design, build and iterate on production ML and Generative AI/LLM systems that support claims validation and automation

Collaborate closely with other Claims data scientists to bring system-level thinking to how models, data and workflows fit together, identifying architectural improvements needed to scale decisioning and reduce time-to-production

Be vocal about the platform and tooling investments needed (monitoring, feedback loops, QA) to achieve AI-driven end to end claims automation

Advocate for robust, scalable, and strategically aligned technical solutions in cross-functional discussions, ensuring current systems and infrastructure contribute to the multi-year vision for automated claims handling

Set a high bar for statistical rigour, experimentation and measurement, helping improve how Claims performance and uncertainty are understood and communicated to senior stakeholders

Who You Are

You think in systems: you can connect the dots between data science, engineering, and product to shape scalable solutions that build on each other over time.

You're confident in challenging assumptions and pushing for the right approach, using strong communication skills to influence stakeholders across seniority levels and disciplines with clear, pragmatic reasoning.

You thrive in ambiguity and change, staying resilient and effective during transitions while bringing structure, clarity, and momentum to complex problem spaces.

You're motivated by real-world impact, partnering closely with cross-functional teams to drive meaningful automation and better customer outcomes across the claims journey.

What You'll Bring

Significant commercial experience delivering end-to-end Machine Learning solutions, from problem framing and experimentation through to production deployment and ongoing monitoring

Hands-on experience building and shipping Generative AI systems in production (not just prototypes), including evaluation, safety/quality considerations, and integration into customer or operational workflows

Strong statistical and modelling foundation, with experience in risk-based decisioning under uncertainty (e.g., fraud, credit, insurance, or other regulated domains)

Proven ability to influence technical direction across Data Science and Engineering, including shaping scalable model/service integration patterns and challenging proposals to drive robust, long-term solutions

Strong stakeholder management skills, with confidence communicating trade-offs and pushing back constructively with Product and Engineering to ensure high-quality outcomes

Perks of the job

Bonus scheme designed to reward high performance

Private medical insurance with Vitality, mental health support with Oliva

Personal learning budget and 2 dedicated L&D days a year

Monthly flexible benefits budget to spend as you choose

4 weeks Work From Anywhere per year

We are able to offer visa sponsorship for this position.

Our process

Initial call with a member from our Talent Team (30 mins)

Past Experience interview with Hiring Manager (60 mins)

Systems Design & Technical interview with a couple of the team (90 mins)

Culture interview (60 mins)

Diversity of thought

We know the best ideas come from having different perspectives in the room - and we're committed to hiring fairly, regardless of background, identity or experience. If you see yourself in this role, we'd encourage you to apply.