Principal ML Engineer (AI)

Location: On-site in London, UK or Lisbon, Portugal

Salary: €12,000–€20,000 per month before taxes; up to €220,000 per year plus equity.

Company

Rent.app is a rapidly growing company improving payment optimisation, underwriting, fraud prevention, marketing efficiency, and business automation after raising $125M across Series A and B funding.

What you will do

• Set the technical direction and own the full lifecycle of machine learning systems, from problem formulation and experimentation through deployment and monitoring.
• Build and improve models for underwriting, credit risk, fraud detection, payment routing, collections, and marketing optimisation.
• Combine traditional statistical and machine learning techniques with foundation models and LLM-based approaches.
• Work directly on the underwriting stack, integrating classical ML with the company’s foundation-model-based systems.
• Mentor engineers and guide production ML development.

Requirements

• Exceptional depth in machine learning and substantial experience building and operating production ML systems.
• Experience with ranking, classification, tree-based models, calibration, deep learning, and LLM systems.
• Strong Python and SQL skills.
• Experience designing scalable training, inference, and model-monitoring infrastructure in a cloud environment.
• AI-native working habits and comfort using modern AI tools for research, development, and experimentation.
• Conversational English and availability for on-site work in London or Lisbon.

Nice to have

• Experience in credit underwriting, lending, payments, fraud, or financial services.

Culture & Benefits

• Official employment.
• Visa and relocation support.
• Supplemental medical coverage and wellness benefits.
• Corporate laptop.
• Equity participation.