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This paper explores a novel paradigm for integrating LLMs into production advertising systems by using a fine-tuned open-source LLM as an ancillary predictor of likely advertisers based on user profiles. This LLM-driven prediction augments candidate generation and provides informative priors to downstream ranking models. The approach demonstrates substantial offline improvements and measurable online business impact in a large-scale production advertising system, validating the utility of LLMs for ads applications.
LLMs can drive significant gains in ad systems, not just as rankers or retrievers, but as complementary predictors that forecast likely advertisers from user profiles.
Recommendation systems power engagement and monetization across feeds, ads, and short-video platforms, but translating the latest advances in Large Language Models into Recommendation Systems (RecSys) gains remains rare, particularly in advertising and production-scale real-world industry setups. Prior real-world LLM successes typically fall into three buckets: (a) generative retrieval that directly predicts the next items for candidate generation, (b) late-stage re-ranking that uses LLMs, and (c) auxiliary signal enrichment with LLMs. We introduce a complementary paradigm for ads: a fine-tuned open-source LLM used not as a ranker, but as an ads-specific ancillary predictor, forecasting likely advertisers from user profiles and histories. This LLM-driven advertiser prediction augments conventional candidate generation and provides informative priors to downstream ranking. Developed in a large-scale production advertising system, our approach produces substantial offline improvements and measurable online business impact, demonstrating that LLM world knowledge and predictive capacity can be efficiently harnessed. Beyond validating LLMs for ads applications, our results show that targeted ancillary predictions can unlock end-to-end gains across both retrieval and late-stage ranking, offering a practical path to LLM-enhanced recommendation at scale.
