ความสำคัญของการแคชการเรียกใช้ LLM

Imagine you look up a word in a dictionary. If you need to look up the same word again, it's faster to remember it than to open the dictionary and find it again.

Caching is like remembering. It stores results of expensive operations so you can reuse them quickly instead of re-doing the work.

Large Language Models (LLMs) often charge per "token" used. Every time your application sends a prompt and receives a response, you pay for the tokens.

• Prompt tokens: The text you send to the LLM.
• Completion tokens: The text the LLM generates back.

Repeatedly asking the same question means repeatedly paying for the same work.

Even if costs weren't an issue, calling an external LLM API takes time. This is called latency.

Network requests, model inference time, and API response processing all contribute to delays. For interactive applications, users expect fast responses.

This is where caching becomes a superpower for LLM applications! Instead of always calling the LLM, we can store its responses for common or identical requests.

When a user asks a question, your app first checks the cache. If the answer is there, great! If not, then it calls the LLM and stores the new response in the cache.

The most direct benefit of caching is cost reduction. By serving cached responses, you avoid sending requests to the LLM API.

This means fewer tokens used, leading to lower bills from your LLM provider. For applications with many users asking similar questions, the savings can be substantial.

Retrieving data from a local cache is significantly faster than making an external network call to an LLM API. We're talking milliseconds versus seconds!

Faster responses lead to a much better user experience. Your application feels snappier and more responsive, which is crucial for engagement.

It's not just LLM responses that benefit from caching! Generating vector embeddings also involves an API call (or local computation) and costs money/time.

If you're frequently embedding the same chunks of text (e.g., user queries or document chunks for retrieval), caching these embeddings can also save costs and speed up your RAG pipeline.

Caching is most effective for LLM calls that are:

• Deterministic: The LLM always gives the same (or very similar) answer for the same prompt.
• Frequent: The same prompt is likely to be asked multiple times.
• Static: The underlying information doesn't change often.

Avoid caching for highly dynamic or personalized responses that change with every request.

Here's a simplified Python example showing the logic of a basic cache for LLM calls. It checks if a prompt is already in our cache dictionary.

In this lesson, we explored the critical reasons for implementing caching in LLM applications. We learned that caching helps:

• Reduce costs: By minimizing redundant LLM API calls.
• Improve performance: By drastically lowering response times for frequent queries.
• Optimize embedding generation: Extending benefits beyond just LLM responses.

Next, we'll dive into different strategies for implementing these caches.