Authentication is one of those things every developer has to deal with. Let’s make it painless and actually understandable. Why Do We Even Need Authentication? Imagine your house. Without a lock, anyone can walk in. Authentication is the digital lock for your app. It answers two questions: Who are you? Should you access this resource? Traditional session-based auth stores user data on the server. That works, but it creates problems at scale (memory usage, sticky sessions, harder horizontal scaling). JWT (JSON Web Token) solves this with stateless authentication . What is JWT? JWT is a compact, self-contained token that securely transmits information between parties as a JSON object. Think of it as a secure digital ID card that the user carries with them. The server issues it once, and the user presents it with every request. The server can verify it without looking up anything in a database.…