Senior ML Engineer

primer.io; United Kingdom; Remote; GBP 95,000 - 130,000; Full time

Job summary

Primer is the unified infrastructure for global payments, enabling finance teams to reduce complexity and capture more revenue through a single platform. You will join as the first Senior ML Engineer to build foundations for ML in payments, collaborating with engineering, data, and product teams to shape how ML adds value.

You will own end-to-end ML features, productionise routing decisions, and mentor others while engaging with customers to validate ideas and drive impact at scale.

Qualifications

• Senior experience in ML engineering, data science, or applied research with production deployments.

Responsibilities

• Own the full lifecycle of ML-powered features from research to deployment and monitoring in production.

Skills

ML engineering

Experiment design

Python programming

MLOps

Communication with stakeholders

Ambiguity tolerance

Mentoring

Education

Bachelor's degree in CS/Math/ML

Tools

scikit-learn

XGBoost

TensorFlow

PyTorch

Keras

Job description

An Introduction to Primer

Primer is the unified infrastructure for global payments. We give finance and payments teams the visibility and control to reduce complexity, improve performance, and capture more revenue - all from a single platform.

Backed by Sofina, Peak XV Partners, ICONIQ, Tencent, Accel, and Balderton, we're building the payments layer the world's best companies rely on.

Watch our showcase >

Read up on our $100m Series C

Learn more about our culture >

Which team will you be joining?

You'll be our first Senior Engineer in ML, working alongside our Staff Engineer to help build the foundations from the ground up. There's no existing DS/ML team yet, so the two of you will shape it together, working closely with engineering, data, and product, who are already exploring how ML can be used in payments. There's a lot still to figure out and a lot to build. You'll work closely with your team's stakeholders to identify where ML can move the needle, and report to engineering leadership while that function takes shape.

What will you be doing?

• Own the full lifecycle of ML-powered features within your initiatives - from independently researching and testing approaches through training, deployment and monitoring in production

• Productionise smart routing decisions across the payment flow, building the ML infrastructure around them as you go - versioning, CI/CD, observability

• Partner closely with product, data and engineering to turn promising use cases into shipped, measured outcomes

• Bring a pragmatic, impact-first mindset to experimentation and model evaluation, rather than chasing the most sophisticated approach

• Mentor other engineers as they pick up ML techniques, sharing how you think about tradeoffs and when to keep things simple

• Talk directly to customers to validate ideas and pressure-test what you're building against real usage

• Help set technical direction within your area, working with your team to prioritise the use cases worth pursuing

• Establish patterns and practices that make ML work reliable and repeatable at Primer, building on foundations rather than defining them alone

What we're looking for

• Senior experience in ML engineering, data science, or applied research, with real production deployments behind you (API, batch, or streaming)

• You think statistically. You can design and run experiments and A/B tests, and report what the results do and don't show

• Strong Python skills and hands‑on experience with ML libraries such as scikit-learn, XGBoost, TensorFlow, PyTorch or Keras

• Solid grounding in modern software engineering, infrastructure and data tooling, and an understanding of the MLOps challenges across the full ML lifecycle. You don't need to have built a platform, but you know what one has to handle

• Familiarity with reinforcement learning (multi-armed or contextual bandits, for example). Production experience with it isn't required, but you need to understand how it works and where it applies

• Cloud experience - AWS preferred; GCP or Azure both fine

• Exposure to payments or e-commerce is a plus, not a prerequisite - you'll build that domain depth on the job

• Comfortable with ambiguity, in the problems and in the process. You can research, develop and productionise independently, and you'll help define how we work as you go

You may not like it here

• You enjoy working in an office setting - we're remote-first, and always will be

• You need a fully mapped‑out roadmap before you start - we're building this function, and there is a lot yet to be defined.