MESS+: Dynamically Learned Inference-Time LLM Routing in Model Zoos with Service Level Guarantees

Fuente: arXiv
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Auteurs principaux: Woisetschläger, Herbert, Zhang, Ryan, Wang, Shiqiang, Jacobsen, Hans-Arno
Format: Preprint
Publié: 2025
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author Woisetschläger, Herbert
Zhang, Ryan
Wang, Shiqiang
Jacobsen, Hans-Arno
author_facet Woisetschläger, Herbert
Zhang, Ryan
Wang, Shiqiang
Jacobsen, Hans-Arno
contents Open-weight large language model (LLM) zoos provide access to numerous high-quality models, but selecting the appropriate model for specific tasks remains challenging and requires technical expertise. Most users simply want factually correct, safe, and satisfying responses without concerning themselves with model technicalities, while inference service providers prioritize minimizing operating costs. These competing interests are typically mediated through service level agreements (SLAs) that guarantee minimum service quality. We introduce MESS+, a stochastic optimization algorithm for cost-optimal LLM request routing while providing rigorous SLA compliance guarantees. MESS+ learns request satisfaction probabilities of LLMs in real-time as users interact with the system, based on which model selection decisions are made by solving a per-request optimization problem. Our algorithm includes a novel combination of virtual queues and request satisfaction prediction, along with a theoretical analysis of cost optimality and constraint satisfaction. Across a wide range of state-of-the-art LLM benchmarks, MESS+ achieves an average of $2\times$ cost savings compared to existing LLM routing techniques.
format Preprint
id arxiv_https___arxiv_org_abs_2505_19947
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle MESS+: Dynamically Learned Inference-Time LLM Routing in Model Zoos with Service Level Guarantees
Woisetschläger, Herbert
Zhang, Ryan
Wang, Shiqiang
Jacobsen, Hans-Arno
Machine Learning
Artificial Intelligence
Systems and Control
I.2; I.2.7; I.2.8
Open-weight large language model (LLM) zoos provide access to numerous high-quality models, but selecting the appropriate model for specific tasks remains challenging and requires technical expertise. Most users simply want factually correct, safe, and satisfying responses without concerning themselves with model technicalities, while inference service providers prioritize minimizing operating costs. These competing interests are typically mediated through service level agreements (SLAs) that guarantee minimum service quality. We introduce MESS+, a stochastic optimization algorithm for cost-optimal LLM request routing while providing rigorous SLA compliance guarantees. MESS+ learns request satisfaction probabilities of LLMs in real-time as users interact with the system, based on which model selection decisions are made by solving a per-request optimization problem. Our algorithm includes a novel combination of virtual queues and request satisfaction prediction, along with a theoretical analysis of cost optimality and constraint satisfaction. Across a wide range of state-of-the-art LLM benchmarks, MESS+ achieves an average of $2\times$ cost savings compared to existing LLM routing techniques.
title MESS+: Dynamically Learned Inference-Time LLM Routing in Model Zoos with Service Level Guarantees
topic Machine Learning
Artificial Intelligence
Systems and Control
I.2; I.2.7; I.2.8
url https://arxiv.org/abs/2505.19947