# Cache Invalidation: Avoiding Stale Cache When Updating System Prompt, Tools, FAQ

> Source: https://sukruyusufkaya.com/en/learn/token-ekonomisi/cache-invalidation-system-prompt-tools-update
> Updated: 2026-05-14T14:44:14.111Z
> Category: Token Ekonomisi & LLM Cost Optimization
> Module: Module 7: Prompt Caching — The Single Biggest Cost Lever of 2026
**TLDR:** You enabled cache in production. One day you need to update the system prompt — old cache is stale. This lesson covers dual-write pattern, gradual rollout, cache versioning, and emergency invalidation.