When NOT to use RAG (lessons from building a Claude-powered support bot)

Every tutorial about building AI chatbots reaches for the same starter pack: vector database, embeddings model, similarity search, RAG. I did too. Then I ran the numbers on prompt caching and threw most of it out. Here's what happened. The setup I'm building a customer support bot for a B2C SaaS product. It hooks into Crisp (live chat), reads incoming customer messages, looks up answers in a knowledge base, and replies — escalating to a human when it can't help. The stack: Bun server (one file,