Principal Machine Learning Engineer

Barcelona, Spain (Hybrid) | Up to €135,000 Base + Bonus (c.€150,000 OTE)

This is an opportunity to join a growing, profitable AI-driven technology business where machine learning is central to the product and commercial strategy. The role offers a rare blend of technical leadership and hands-on engineering, allowing you to shape the future direction of ML systems while solving complex challenges at scale.

The Company

They are an established technology scale-up that develops advanced machine learning solutions to power highly personalised digital experiences for millions of users worldwide. Operating internationally, the business has grown significantly in recent years and continues to invest heavily in its data and AI capabilities.

Their machine learning teams work on large-scale real-time systems where model performance directly impacts commercial outcomes. With a collaborative engineering culture and strong leadership support, they offer an environment where innovation and experimentation are encouraged.

The Role





As a Principal Machine Learning Engineer, you will provide technical leadership across the machine learning function while remaining closely involved in model development and production systems.

Key responsibilities include:
- Defining technical direction for machine learning systems and frameworks.
- Designing, developing and optimising machine learning models in a large-scale production environment.
- Leading the development of recommendation engines, bidding algorithms and audience targeting systems.
- Building mobile attribution models and solutions focused on customer lifetime value and churn prediction.
- Driving best practice across MLOps, model monitoring, observability and automated retraining.
- Enhancing machine learning infrastructure, experimentation platforms and deployment processes.
- Partnering with engineering leaders and business stakeholders to align machine learning initiatives with commerci

📌 Principal ML Engineer 199877 (Barcelona)
🏢 Harnham
📍 Barcelona