Engineering6 min read · 1,203 wordsAugust 3, 2026

Model Routing: Automatically Choosing the Cheapest Model That Works

The use of Large Language Models (LLMs) like GPT-4 has become increasingly prevalent in various applications, from chatbots to content generation. However, the cost of using these models can be prohibitively expensive, especially when using the most advanced models like GPT-4 for every task. For…

The use of Large Language Models (LLMs) like GPT-4 has become increasingly prevalent in various applications, from chatbots to content generation. However, the cost of using these models can be prohibitively expensive, especially when using the most advanced models like GPT-4 for every task. For instance, using GPT-4 for a simple task like text classification can cost around $0.05 per request, which may not seem like a lot, but can quickly add up to $1,500 per month for a moderate-traffic application. This is because GPT-4 is a high-end model that is capable of handling complex tasks, but is often overkill for simpler tasks. With Cognocient, you can automatically route requests to the cheapest model that can handle the task, reducing costs by up to 70%. For example, Cognocient can route simple text classification tasks to a cheaper model like GPT-3, which costs around $0.01 per request, resulting in a monthly cost of $300.

The Model Selection Problem

The model selection problem arises when you have multiple LLMs with different capabilities and price points, and you need to choose the right model for each task. This can be a daunting task, especially when you have a large number of tasks with varying complexity levels. Using a high-end model like GPT-4 for every task can result in significant cost overruns, while using a cheaper model for complex tasks can result in poor performance. For instance, a company that uses GPT-4 for all its tasks may end up spending $10,000 per month, while a company that uses a cheaper model for all its tasks may end up with poor performance and dissatisfied customers. Cognocient solves this problem by providing a smart routing system that automatically chooses the cheapest model that can handle each task. With Cognocient, you can define routing rules based on task complexity, model capability, and cost, and the system will automatically route requests to the right model.

Task Complexity vs Model Capability

Task complexity and model capability are two important factors to consider when selecting an LLM. Task complexity refers to the difficulty level of the task, while model capability refers to the ability of the model to handle complex tasks. For example, a task like text classification may require a model with high accuracy and precision, while a task like language translation may require a model with high fluency and coherence. Cognocient provides a range of models with different capabilities, from simple models like GPT-3 to advanced models like GPT-4. With Cognocient, you can define routing rules that match the task complexity with the right model capability, ensuring that each task is handled by the most suitable model. For instance, you can define a rule that routes all text classification tasks to GPT-3, while routing all language translation tasks to GPT-4.

Building Routing Rules in Cognocient

Building routing rules in Cognocient is a straightforward process that involves defining the task complexity, model capability, and cost. You can define routing rules based on various factors, such as task type, input size, and output size. For example, you can define a rule that routes all tasks with input size less than 100 tokens to GPT-3, while routing all tasks with input size greater than 100 tokens to GPT-4. Cognocient provides a simple and intuitive interface for defining routing rules, and you can easily test and refine your rules using the Cognocient dashboard. With Cognocient, you can also define fallback chains that try smaller models first and escalate to larger models only if needed.

Fallback Chains

Fallback chains are an important feature in Cognocient that allows you to define a sequence of models to try for each task. For example, you can define a fallback chain that tries GPT-3 first, and if it fails, tries GPT-4. This ensures that each task is handled by the most suitable model, and you can avoid using expensive models for simple tasks. Fallback chains can be defined based on various factors, such as task type, input size, and output size. With Cognocient, you can easily define and manage fallback chains using the Cognocient dashboard. For instance, you can define a fallback chain that tries the following models in sequence:

ModelInput SizeOutput Size
GPT-3< 100 tokens< 100 tokens
GPT-4>= 100 tokens>= 100 tokens
This ensures that small tasks are handled by GPT-3, while larger tasks are handled by GPT-4.

Cost Savings from Routing

The cost savings from routing can be significant, especially for applications with high traffic volumes. By automatically routing requests to the cheapest model that can handle the task, Cognocient can reduce costs by up to 70%. For example, a company that uses GPT-4 for all its tasks may spend $10,000 per month, while a company that uses Cognocient to route requests to the cheapest model may spend only $3,000 per month. This represents a cost savings of $7,000 per month, or 70% of the original cost. With Cognocient, you can achieve significant cost savings without compromising on performance.

Real-World Example

Here is a real-world example of how Cognocient can be used to reduce costs:

# Before - using GPT-4 for all tasks
client = OpenAI(base_url="https://api.openai.com/v1")
response = client.post("/completions", json={"prompt": "Hello, world!"})

# After - using Cognocient to route requests to the cheapest model
client = OpenAI(base_url="https://api.cognocient.com/v1")
response = client.post("/completions", json={"prompt": "Hello, world!"})

In this example, the base_url is changed to point to the Cognocient API, which automatically routes requests to the cheapest model that can handle the task. This results in significant cost savings without compromising on performance.

When NOT to Route

There are certain tasks where model quality is the product, and routing to a cheaper model may not be desirable. For example, in applications where high-end models are required to achieve high accuracy and precision, routing to a cheaper model may compromise on performance. In such cases, Cognocient provides the option to bypass routing and use a specific model for the task. This ensures that the task is handled by the most suitable model, even if it is more expensive. With Cognocient, you can easily define exceptions to routing rules and ensure that critical tasks are handled by the right model.

Key Takeaways

  • Cost Savings: Cognocient can reduce costs by up to 70% by automatically routing requests to the cheapest model that can handle the task.
  • Model Capability: Cognocient provides a range of models with different capabilities, from simple models like GPT-3 to advanced models like GPT-4.
  • Fallback Chains: Cognocient allows you to define fallback chains that try smaller models first and escalate to larger models only if needed.

Try Cognocient Free

Most teams spend an average of $5,000 per month on LLMs, with up to 70% of that cost being wasted on unnecessary model usage. Cognocient gives you a smart routing system that automatically chooses the cheapest model that can handle each task, reducing costs by up to 70% and ensuring that each task is handled by the most suitable model.

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