EP025: Prompt Caching Deep Dive — How to Save 80% on Repeated API Calls

If you're making repeated API calls with large system prompts, you're throwing money away. We go deep on prompt caching across OpenAI, Anthropic Claude, Google Gemini, and DeepSeek — how each implementation works, the real pricing differences (from 50% to 90% off), and five concrete patterns for maximizing cache efficiency in production. Plus the gotchas around cache invalidation and why an API gateway lets you route to the best cache pricing for your workload.