I've been building a publishing tool , and I chose Fastify for the backend. The reasoning was simple: official plugins (jwt, cookie, cors) cover all the essentials, the performance reputation is solid, and TypeScript support is complete. Now that the P0 end-to-end flow is running, here are the pitfalls I hit along the way. 1. The second argument to register is not what you think The most subtle pitfall. I wanted to protect a whole group of business routes with authentication, s...