Prompt Caching for Anthropic and OpenAI Models: Building Cost-Efficient AI Systems

Prompt caching has emerged as a crucial optimization technique for production AI systems, allowing repeated prompt segments like system instructions and tool schemas to be reused across requests. Both Anthropic and OpenAI now support this technology, with cached tokens costing roughly 90% less than regular tokens—OpenAI's cached input tokens cost $0.125 per million compared to $1.25 for standard tokens. This creates dramatic cost savings of 70-90% for applications with large static prompts, potentially saving tens of thousands of dollars monthly for high-volume systems.