Principal Machine Learning EngineerLocation: Barcelona (Remote / Hybrid - Fully Remote or 2 Days in the Office)Salary: €135,000 Base + €15,000 Bonus (OTE €150,000)THE COMPANYThis profitable French Ad Tech 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.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 ROLEAs 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 scaleProven technical leadership, defining architecture and technical direction while remaining hands-onStrong experience developing recommendation systems, audience targeting models, LTV or churn modelsExperience building robust MLOps platforms including model monitoring, automated retraining and production deploymentExcellent Python and modern machine learning framework experience (Py Torch, Tensor Flow or similar)Strong software engineering and distributed systems knowledgeAbility to communicate complex technical concepts to senior stakeholdersAd Tech or Demand Side Platform (DSP) experience highly desirablePh D 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 years4.5-day working week with Friday afternoons offFully remote working or hybrid (2 days per week if based near an office)Two company meet-ups each yearWork directly alongside the CTOJoin a profitable, high-growth international AI business with significant technical ownership opportunities INTERVIEW PROCESS 15-minute HR conversationTake-home technical assessmentTechnical interview and assessment review with senior ML engineersCTO interviewExecutive Committee interview #J-*****-Ljbffr

📌 Manager, Machine Learning Engineering (Barcelona)
🏢 Harnham
📍 Barcelona