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arXiv · 2510.20260

Balancing Fine-tuning and RAG: A Hybrid Strategy for Dynamic LLM Recommendation Updates

Changping Meng·Hongyi Ling·Jianling Wang·Yifan Liu·Shuzhou Zhang·Dapeng Hong·Mingyan Gao·Onkar Dalal·Ed Chi·Lichan Hong·Haokai Lu·Ningren Han
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Abstract

Large Language Models (LLMs) empower recommendation systems through their advanced reasoning and planning capabilities. However, the dynamic nature of user interests and content poses a significant challenge: While initial fine-tuning aligns LLMs with domain knowledge and user preferences, it fails to capture such real-time changes, necessitating robust update mechanisms. This paper investigates strategies for updating LLM-powered recommenders, focusing on the trade-offs between ongoing fine-tuning and Retrieval-Augmented Generation (RAG). Using an LLM-powered user interest exploration system as a case study, we perform a comparative analysis of these methods across dimensions like cost, agility, and knowledge incorporation. We propose a hybrid update strategy that leverages the long-term knowledge adaptation of periodic fine-tuning with the agility of low-cost RAG. We demonstrate through live A/B experiments on a billion-user platform that this hybrid approach yields statistically significant improvements in user satisfaction, offering a practical and cost-effective framework for maintaining high-quality LLM-powered recommender systems.

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Changping Meng, Hongyi Ling, Jianling Wang, Yifan Liu, Shuzhou Zhang, Dapeng Hong, Mingyan Gao, Onkar Dalal, Ed Chi, Lichan Hong, Haokai Lu, Ningren Han. 2025-10-23. Balancing Fine-tuning and RAG: A Hybrid Strategy for Dynamic LLM Recommendation Updates. https://doi.org/10.1145/3705328.3748105

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