Senior ML Engineer

📋 Job Overview

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.

🏢 About 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.

🎯 The Role

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.

✅ Key Responsibilities

• 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

📌 Required Qualifications

• 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

⭐ Desirable Experience

• Experience in payments or e-commerce domain

🎁 Benefits

• 🌍 Fully remote and globally distributed
• 💰 Competitive share options
• 🌴 Uncapped holiday, with 25 days minimum to be taken
• 🗣️ Co-working space access across major cities
• 📅 Workations & Company Retreat
• 💻 The best equipment for your role
• 🏠 £500 towards your home office setup
• 🔎 Generous learning budget
• 🏥 Private Medical Insurance
• 📈 A broad set of additional perks and benefits (depending on location)

🛂 Visa & Eligibility

Primer is committed to the equal treatment of all current and prospective employees and adopts a zero-tolerance approach to discrimination, regardless of age, disability, sex, sexual orientation, pregnancy and maternity, religion or belief, gender reassignment, marriage and civil partnership, or nationality.