Beyond Two Towers: Launching the 3-Tower Engagement Co-Train Model (Part 2)

Authors: Longyu Zhao (Staff Machine Learning Engineer), Gwendolyn Zhao (Staff Machine Learning Engineer), Peng Yan (Senior Machine Learning Engineer), Yuanlu Bai (Senior Machine Learning Engineer), Yuan Wang (Senior Machine Learning Engineer), Yao Cheng (Staff Machine Learning Engineer), Ang Xu (Principal Machine Learning Engineer), Zhaohong Han (Manager II, Ads Lightweight Ranking)

Introduction

Previously¹, we launched the next-generation serving stack for standard ads, which we call Nexus. Nexus decoupled candidate generation from scoring and moved us beyond the classic two-tower-only world, enabling richer model architectures while still meeting stringent latency and cost constraints.