Senior Principal Machine Learning Engineer - Optimization

Role: Hybrid in Redwood City, CA. (Will consider Remote for the right candidate) Must have: Experience building large-scale prediction or optimization systems PubMatic is the leading AI-powered ad tech company delivering measurable advertising performance through an intelligent, unified platform that connects buyers, publishers, data partners, and commerce media across CTV, mobile app, and omnichannel environments. About the Role: We are looking for a Senior Principal Machine Learning Engineer to help build the next generation of performance optimization capabilities for PubMatic’s Activate platform. This role is focused on applying machine learning, prediction, ranking, calibration, experimentation, and optimization techniques to improve campaign outcomes across performance advertising goals such as CTR, VCR, CPC, CPA, and ROAS. The ideal candidate has strong ML fundamentals and experience building large-scale production models or optimization systems. What You'll Do: Build and improve machine learning models for campaign optimization, prediction, ranking, bidding, forecasting, and calibration. Develop models and algorithms that improve advertiser outcomes while balancing spend delivery, cost efficiency, campaign goals, marketplace dynamics, and system constraints. Work on large-scale ML systems using signals from auctions, impressions, clicks, video events, conversions, users, context, inventory, campaigns, and marketplace feedback. Design and improve CTR, CVR, VCR, CPA, ROAS, app-install, user-value, and campaign-performance models. Develop bidding, pacing-aware optimization, ranking, exploration, and value-estimation approaches for performance advertising. Improve model calibration, online/offline evaluation, experimentation, observability, and production feedback loops. Reason through sparse conversions, delayed feedback, biased logs, cold-start campaigns, attribution noise, and online/offline metric mismatch. Partner with performance advertising signal engineers to define model-ready features, labels, attribution windows, negative examples, training datasets, and online serving requirements. Partner with engineering, product, analytics, and platform teams to translate model outputs into real-time decisioning systems. Help evolve Activate from a media buying execution platform into a performance optimization platform. Provide technical leadership and mentorship to engineers and applied scientists working on performance optimization problems. 10+ years of experience building production machine learning, ranking, recommendation, prediction, optimization, ads, marketplace, bidding, or pricing systems.