---
title: "What changes to an OpenAI prompt still allow a cache hit?"  
description: "What changes to an OpenAI prompt still allow a cache hit?"  
author: "Katherine Sullivan"  
published: 2026-10-23  
updated: 2026-10-23  
canonical: https://www.mindstick.com/forum/162897/what-changes-to-an-openai-prompt-still-allow-a-cache-hit  
category: "Prompt Caching"  
tags: ["OpenAI API", "Prompt Caching", "API performance"]  
reading_time: 1 minute  

---

# What changes to an OpenAI prompt still allow a cache hit?

I’m trying to use prompt caching for a request that has a long set of shared instructions followed by user-specific details. The shared part stays mostly the same, but a few values and occasional instruction updates can change.

How sensitive is a cache hit to edits near the beginning of the prompt? I’m especially interested in whether there’s a practical way to organize a **static prompt prefix** without making the request awkward to maintain. If you’ve measured this in an app, what changes affected your cache-hit rate?


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Original Source: https://www.mindstick.com/forum/162897/what-changes-to-an-openai-prompt-still-allow-a-cache-hit

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