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This paper introduces DCEO, a novel framework for optimizing item-level proxy scores in e-commerce search systems to better align with long-term user objectives like cumulative purchases and GMV. By employing an actor-critic approach, DCEO dynamically generates context-dependent fusion weights, improving the alignment of item-level scores with user-level goals and enhancing personalization. The method was validated through extensive offline experiments and a successful deployment in a large-scale system, achieving a 0.36% increase in GMV compared to traditional methods during a 41-day A/B test.
DCEO outperforms traditional GMV proxies by directly optimizing causal effects, leading to a significant boost in long-term user value in e-commerce search.
Industrial e-commerce search systems ultimately aim to optimize the user-level long-term objective, such as n-day cumulative purchases or gross merchandise value (GMV) per user. However, such objectives are defined at the user level, whereas search ranking is based on item-level scores within each request. Existing methods typically bridge this granularity gap through manually designed multi-objective fusion, where predictions of multiple item-level objectives, such as clicks, carts, purchases, and transaction value, are combined into a ranking score that serves as a proxy for the ultimate objective. Such hand-crafted fusion schemes rely on a small set of manually tuned weights, limiting fine-grained personalization and leading to suboptimal alignment with the ultimate objective. In this paper, we propose DCEO (Direct Causal Effect Optimization), a data-driven framework for learning item-level proxy scores that are better aligned with the ultimate objective. We first aggregate the item-level proxy scores into a user-level proxy metric and quantify its alignment with the ultimate objective using a relative causal effect. We then develop an actor-critic framework, where the critic estimates the ultimate objective for a given user-level proxy metric, and the actor dynamically generates context-dependent fusion weights over multiple objectives to construct the item-level proxy scores and is trained to directly optimize the relative causal effect. Extensive offline experiments and analyses demonstrate the effectiveness and interpretability of DCEO. In addition, DCEO has been deployed in a large-scale industrial e-commerce search system, outperforming the conventional GMV proxy by 0.36% in GMV in a 41-day online A/B test.
