Principal Machine Learning Engineer Location:

Barcelona (Remote / Hybrid - Fully Remote or 2 Days in the Office)

Salary:

€135,000 Base + €15,000 Bonus (OTE €150,000)

THE COMPANY This profitable French AdTech scale-up is transforming digital advertising through machine learning. By building AI-powered technology that determines which users are most likely to engage with an advert, they help leading mobile apps drive customer acquisition and re-engagement through highly targeted advertising.

Following approximately 60% growth over the past two years, the business has expanded to around 140 employees across offices in Paris, Barcelona, Seoul and San Francisco, with more than 25 open positions supporting continued international growth.

You’ll be joining a highly technical engineering team, working directly alongside the CTO to shape the future of machine learning across the business.

THE ROLE As a Principal Machine Learning Engineer, you’ll define the technical direction of large-scale production machine learning systems while remaining hands-on throughout the full model lifecycle. This is an individual contributor leadership role focused on delivering complex technical projects rather than managing people.

You’ll lead end-to-end machine learning initiatives across recommendation systems, audience targeting, bidding optimisation and customer lifecycle modelling, partnering closely with senior engineering and business stakeholders to translate commercial objectives into production-ready AI solutions. The role combines technical strategy,



platform engineering and applied machine learning within a high-scale real-time environment.

YOUR SKILLS AND EXPERIENCE

Extensive experience building and deploying production machine learning systems at scale

Proven technical leadership, defining architecture and technical direction while remaining hands-on

Strong experience developing recommendation systems, audience targeting models, LTV or churn models

Experience building robust MLOps platforms including model monitoring, automated retraining and production deployment

Excellent Python and modern machine learning framework experience (PyTorch, TensorFlow or similar)

Strong software engineering and distributed systems knowledge

Ability to communicate complex technical concepts to senior stakeholders

AdTech or Demand Side Platform (DSP) experience highly desirable

PhD in a STEM discipline is advantageous

THE BENEFITS

€135,000 base salary plus approximately €15,000 annual bonus (OTE €150,000)

Longevity bonus every two years

4.5-day working week with Friday afternoons off

Fully remote working or hybrid (2 days per week if based near an office)

Two company meet-ups each year

Work directly alongside the CTO

Join a profitable, high-growth international AI business with significant technical ownership opportunities

INTERVIEW PROCESS

15-minute HR conversation

Take-home technical assessment

Technical interview and assessment review with senior ML engineers

CTO interview

Executive Committee interview

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📌 Principal Machine Learning Engineer - 199877 (Barcelona)
🏢 Harnham
📍 Barcelona