If you’re serious about getting hired as a backend or full-stack developer — or building real-world applications — you cannot skip authentication. Anyone can build a simple to-do list. But employers and real products care about one key question: Can you securely handle users? Can you securely store their data? Can you securely retrieve it? Can you safely send it to the frontend? In this tutorial, we’ll build the simplest and cleanest JWT authentication setup using Express and MongoDB. ✔ User reg