Fraud Machine Learning Engineer

Harnham is a Series E fintech company focused on using machine learning to combat real-time fraud in e-commerce. They are seeking a Senior ML Engineer / Applied Scientist to design, experiment, and take ownership of models that approve or decline transactions at a global scale.

Responsibilities:

• Building ensemble decision systems combining multiple models into a single fraud signal
• Designing offline evaluation frameworks that mirror production reality
• Running end-to-end experimentation (not tuning APIs)

Requirements:

• 4–8+ years in production ML
• Strong grounding in stats + experimentation design
• Experience building models from scratch, not just fine-tuning
• Comfort working in distributed systems (Spark)
• Python, SQL, Spark (non-negotiable)
• fraud ML
• payments
• trust & safety
• high-scale experimentation environments