Semantic Caching for Production LLM APIs in September 2026: When to Cache Embeddings vs. Exact Prompts
Semantic Caching for Production LLM APIs in September 2026: When to Cache Embeddings vs. Exact Prompts Semantic caching can reduce the cost and response time of a production LLM application, but it is not simply a matter of storing every answer and returning it later. A reliable cache must decide when two requests are equivalent enough to share a response, when a prompt must match exactly, how long an answer remains valid, and what information must never be reused across users. In September 2026, these decisions matter more than ever as applications combine large language models with retrieval, tools, structured output, and frequently changing business data. Image: mikemacmarketing / photo on flickr via Wikimedia Commons (CC BY 2.0) Image: Midjourney; prompt suggested by Grok via Wikimedia Commons (Public domain) Semantic caching is most useful when an application receives requests that are different in wording but similar in intent. For example, “How do I reset ...