Senior ML Engineer

About the role

Primer is building the unified infrastructure for global payments and is looking for its first Senior Machine Learning Engineer. You will work alongside a Staff Engineer to create the ML foundation from scratch, collaborating with product, data and engineering teams to turn payment‑related use cases into measurable outcomes.

Key responsibilities

• Own the full lifecycle of ML‑powered features, from research and testing to training, deployment and production monitoring.
• Productionise smart routing decisions across the payment flow, building versioned, CI/CD‑enabled, observable ML infrastructure.
• Partner with product, data and engineering to translate promising use cases into shipped, measured outcomes.
• Mentor engineers on ML techniques, trade‑offs and simplicity.
• Engage directly with customers to validate ideas and test real‑world usage.
• Help set technical direction, prioritize use cases and establish repeatable ML practices.

Required profile

• Senior experience in ML engineering, data science or applied research with production deployments (API, batch or streaming).
• Strong statistical mindset; able to design experiments, A/B tests and interpret results.
• Solid software engineering background, familiar with modern infrastructure, data tooling and MLOps challenges.
• Comfortable working in ambiguous environments and defining processes independently.

Required skills

• Python
• scikit‑learn
• XGBoost
• TensorFlow
• PyTorch
• Keras
• AWS (preferred)
• GCP or Azure
• Understanding of reinforcement learning concepts (e.g., multi‑armed or contextual bandits)

What we offer

• Fully remote, globally distributed work environment
• Competitive share options
• Uncapped holiday with a minimum of 25 days
• Co‑working space access in major cities
• Workations and annual company retreat
• £500 home‑office setup allowance
• Generous learning budget and private medical insurance