Principal ML Engineer

We're looking for a Principal Machine Learning Engineer to join Rent.app, fresh off 125M Series A + B funding. Rent is going through extensive growth and wants to dramatically improve payment optimisation, underwriting, fraud prevention, marketing efficiency and business automation.

You will

• Set the technical direction and own the full lifecycle of ML systems, from problem formulation and experimentation to deployment and monitoring.
• Build and improve models across underwriting, credit risk, fraud detection, payment routing, collections and marketing optimisation, combining traditional statistical/ML techniques with foundation models and LLM-based approaches.
• Work directly on the underwriting stack, where classical ML and the company's own foundation-model-based systems operate together, and mentor engineers along the way.

Requirements

• Exceptional depth in machine learning, with substantial experience building and operating ML systems in production, including both traditional ML (ranking, classification, tree-based models, calibration) and modern deep learning/LLM systems.
• Strong Python and SQL skills, and experience designing scalable training, inference and model-monitoring infrastructure in a cloud environment.
• AI-native working habits – comfort using modern AI tools to accelerate research, development and experimentation.
• Conversational English.
• Experience in credit underwriting, lending, payments, fraud or financial services is a major plus.
• London, UK or Lisbon, Portugal (on-site).

We offer

• Up to €220k/year salary + equity; higher figures can be negotiated.
• Official employment, visa and relocation help, supplemental medical coverage, wellness benefits, corp. laptop, etc.