Prompt caching is the idea that if a large portion of your prompt stays the same across requests, the system may be able to reuse earlier computation instead of recomputing everything from scratch.
This matters most when you repeatedly send:
- long instructions
- large reference documents
- stable system prompts
- repeated examples
Why it matters
Caching can improve:
- latency
- cost efficiency
- throughput for repeated workflows
It is especially relevant in products where the prompt frame stays stable but the user-specific input changes each time.
The exact behavior depends on the provider and runtime, but the broader lesson is simple: prompt design affects not just quality, but also operational efficiency.