How I Cut My AI Bill by Caching LLM Responses in Node.js

I built an LLM caching library to test what AI-assisted development actually looks like I've been spending my evenings on a personal side project - just learning by building. The latest experiment was wiring up an AI agent into it. While testing, I caught myself sending almost the same prompts over and over. Same intent, slightly different wording. And every test run cost me real money. Then a thought hit me: if I'm doing this while testing, real users in production absolutely will too. The first 1000 users of any AI chatbot mostly ask the same handful of questions.