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AI Glossary · Concepts

What is Model Routing?

Model Routing

Model routing sends each request to the model best suited to it, usually by cost, speed or quality: a cheaper model for easy requests and a stronger, more expensive one for hard requests. A router makes that choice per request instead of sending everything to one model.

Also known as: LLM routing

· Chain of Thought

AI InfrastructureAI Engineering

  • 2 explainers
  • 3 episodes
  • 2 guest clips
  • 2 sources

A customer-support assistant is the simple case. “Where is my order?” can go to a small, cheap model; a refund dispute with a long email thread can go to a larger one. The router that makes the call can be a fixed rule (by task type or prompt length), a small classifier trained to predict which model will answer well, or a cascade that tries the cheap model first and escalates when its answer looks weak. Routing between whole models is different from the router inside a mixture of experts, which picks sub-networks within a single model for each token.

It matters because most products receive a wide mix of requests, and paying frontier-model prices for every one of them is expensive. Research such as RouteLLM and FrugalGPT reports large savings with little or no quality loss on the tasks those papers tested. Those are benchmark results, not guarantees. A router is only as good as the evaluation that tells it which model handles which kind of request; a bad one quietly sends hard questions to a weak model.

In episode 44 at 18:13, Cisco’s Jeetu Patel predicts that enterprises will run many models “in conjunction with one another with an intelligent routing layer,” so that certain queries go to certain models because they cost less to serve (18:38). That is his forecast for the enterprise market, not a measured result.

In episode 59 at 20:02, Superhuman’s Loïc Houssier says his platform team owns “the router”: which LLM to use in which use case and how to switch from one LLM to another, built alongside the evals infrastructure that feature teams rely on. Galileo was the episode’s presenting sponsor; the read is at 1:22.

Hear it from the guest

“Multiple models being used in conjunction with one another with an intelligent routing layer”
“Which LLM to use in what use case, how to flip from one LLM to the other LLM”
Watch on YouTube

Quotes lightly edited to remove filler words.

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