Hybrid Principal ML Engineer — Paris/Barcelona

Harnham is seeking a Principal Machine Learning Engineer for a high-growth AdTech scale-up with ML at the heart of the product. You will report to the CTO, shape technical strategy, and lead cross-team ML initiatives while staying hands-on in model development that powers real-time bidding and attribution.

You will guide ML direction, design production systems, mentor engineers and drive MLOps and observability, aligning technical work with commercial goals across global teams.

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