Mastering Efficiency: The Power of Prompt Caching in Large Language Models

Jason Bell
3 min readFeb 28, 2024

Large Language Models (LLMs) such as GPT (Generative Pre-trained Transformer) have revolutionised the way we interact with technology.

These models have found applications across various domains, including natural language processing, content creation, and even in generating code. However, the computational resources required to run these models can be substantial, especially for applications with high user interaction rates. This is where the technique of prompt caching comes into play, offering a path towards more efficient and sustainable AI operations.

What is Prompt Caching?

Prompt caching is a technique designed to optimise the performance and reduce the computational cost of running Large Language Models. At its core, prompt caching involves storing the responses of LLMs to specific prompts or inputs. When the model receives a prompt it has encountered before, it can retrieve the stored response instead of processing the prompt from scratch. This not only saves on computational resources but also significantly speeds up the response time.

How Does Prompt Caching Work?

The process of prompt caching can be broken down into a few key steps:

Prompt Identification: The system identifies and hashes incoming prompts.
Cache Lookup: It then checks if the hash of the current prompt exists in the cache.
Response Retrieval: If a match is found, the cached response is retrieved and returned to the user.
Processing and Caching: If no match is found, the LLM processes the prompt, and the response, along with the prompt’s hash, is stored in the cache for future use.

This process requires a well-designed caching strategy to balance between cache size, retrieval speed, and the freshness of the cached responses.

Benefits of Prompt Caching

Reduced Latency: By retrieving responses from a cache, the latency associated with generating a response is significantly reduced.
Lower Computational Costs: It decreases the need for repeated computations, saving on CPU and GPU usage, and, by extension, energy consumption.
Improved User Experience: Faster response times lead to a smoother and more engaging user experience.
Scalability: Caching allows for better scalability as it reduces the incremental resources required to handle additional requests.

Real-World Applications and Case Studies

Customer Service Chatbots

One of the most common applications of LLMs is in customer service chatbots. These chatbots often encounter repetitive queries. With prompt caching, responses to common questions can be cached, leading to instant replies and reduced server load. A notable example is a telecom company that implemented prompt caching in their customer service chatbot, resulting in a 40% decrease in response time and a significant reduction in operational costs.

Code Generation Tools

Code generation tools like GitHub Copilot utilise LLMs to assist developers by suggesting code snippets based on the context provided by the user. Given the repetitive nature of certain coding tasks, prompt caching can be particularly beneficial. For instance, caching responses to common programming queries can drastically improve the tool’s efficiency, making the coding process faster and more seamless for developers.

Content Recommendation Engines

LLMs are increasingly used in content recommendation engines to analyse user preferences and suggest personalised content. By caching responses related to popular content or common user profiles, these engines can provide instant recommendations, enhancing user engagement and satisfaction.

Challenges and Considerations

While prompt caching presents numerous benefits, it also poses certain challenges. These include managing cache size and ensuring the relevance of cached responses over time. Additionally, privacy and security concerns arise when caching sensitive information, necessitating robust data handling and security measures.


Prompt caching stands out as a pivotal technique in enhancing the efficiency and sustainability of Large Language Models. By intelligently caching and reusing responses, it paves the way for faster, more cost-effective, and scalable AI applications.

As LLMs continue to permeate various aspects of technology and everyday life, leveraging techniques like prompt caching will be crucial in realising their full potential while addressing the computational challenges they bring.



Jason Bell

A polymath of ML/AI, expert in container deployments and engineering. Author of two machine learning books for Wiley Inc.