Efficient Retrieval Scaling with Hierarchical Indexing for Large Scale Recommendation

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Main Authors: Fu, Dongqi, Rangadurai, Kaushik, Lu, Haiyu, Pu, Yunchen, Yuan, Siyang, Huang, Minhui, Liu, Yiqun, Ghasemiesfeh, Golnaz, He, Xingfeng, Xu, Fangzhou, Cui, Andrew, Viswanathan, Vidhoon, Yang, Lin, Wang, Liang, Yang, Jiyan, Sun, Chonglin
Format: Preprint
Published: 2026
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author Fu, Dongqi
Rangadurai, Kaushik
Lu, Haiyu
Pu, Yunchen
Yuan, Siyang
Huang, Minhui
Liu, Yiqun
Ghasemiesfeh, Golnaz
He, Xingfeng
Xu, Fangzhou
Cui, Andrew
Viswanathan, Vidhoon
Yang, Lin
Wang, Liang
Yang, Jiyan
Sun, Chonglin
author_facet Fu, Dongqi
Rangadurai, Kaushik
Lu, Haiyu
Pu, Yunchen
Yuan, Siyang
Huang, Minhui
Liu, Yiqun
Ghasemiesfeh, Golnaz
He, Xingfeng
Xu, Fangzhou
Cui, Andrew
Viswanathan, Vidhoon
Yang, Lin
Wang, Liang
Yang, Jiyan
Sun, Chonglin
contents The increase in data volume, computational resources, and model parameters during training has led to the development of numerous large-scale industrial retrieval models for recommendation tasks. However, effectively and efficiently deploying these large-scale foundational retrieval models remains a critical challenge that has not been fully addressed. Common quick-win solutions for deploying these massive models include relying on offline computations (such as cached user dictionaries) or distilling large models into smaller ones. Yet, both approaches fall short of fully leveraging the representational and inference capabilities of foundational models. In this paper, we explore whether it is possible to learn a hierarchical organization over the memory of foundational retrieval models. Such a hierarchical structure would enable more efficient search by reducing retrieval costs while preserving exactness. To achieve this, we propose jointly learning a hierarchical index using cross-attention and residual quantization for large-scale retrieval models. We also present its real-world deployment at Meta, supporting daily advertisement recommendations for billions of Facebook and Instagram users. Interestingly, we discovered that the intermediate nodes in the learned index correspond to a small set of high-quality data. Fine-tuning the model on this set further improves inference performance, and concretize the concept of "test-time training" within the recommendation system domain. We demonstrate these findings using both internal and public datasets with strong baseline comparisons and hope they contribute to the community's efforts in developing the next generation of foundational retrieval models.
format Preprint
id arxiv_https___arxiv_org_abs_2604_12965
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Efficient Retrieval Scaling with Hierarchical Indexing for Large Scale Recommendation
Fu, Dongqi
Rangadurai, Kaushik
Lu, Haiyu
Pu, Yunchen
Yuan, Siyang
Huang, Minhui
Liu, Yiqun
Ghasemiesfeh, Golnaz
He, Xingfeng
Xu, Fangzhou
Cui, Andrew
Viswanathan, Vidhoon
Yang, Lin
Wang, Liang
Yang, Jiyan
Sun, Chonglin
Information Retrieval
The increase in data volume, computational resources, and model parameters during training has led to the development of numerous large-scale industrial retrieval models for recommendation tasks. However, effectively and efficiently deploying these large-scale foundational retrieval models remains a critical challenge that has not been fully addressed. Common quick-win solutions for deploying these massive models include relying on offline computations (such as cached user dictionaries) or distilling large models into smaller ones. Yet, both approaches fall short of fully leveraging the representational and inference capabilities of foundational models. In this paper, we explore whether it is possible to learn a hierarchical organization over the memory of foundational retrieval models. Such a hierarchical structure would enable more efficient search by reducing retrieval costs while preserving exactness. To achieve this, we propose jointly learning a hierarchical index using cross-attention and residual quantization for large-scale retrieval models. We also present its real-world deployment at Meta, supporting daily advertisement recommendations for billions of Facebook and Instagram users. Interestingly, we discovered that the intermediate nodes in the learned index correspond to a small set of high-quality data. Fine-tuning the model on this set further improves inference performance, and concretize the concept of "test-time training" within the recommendation system domain. We demonstrate these findings using both internal and public datasets with strong baseline comparisons and hope they contribute to the community's efforts in developing the next generation of foundational retrieval models.
title Efficient Retrieval Scaling with Hierarchical Indexing for Large Scale Recommendation
topic Information Retrieval
url https://arxiv.org/abs/2604.12965