Core REST Principles: Statelessness & CORS Explained | MERN Stack Series #3

This is Video 3 of the REST API Mastery series — where we deep dive into Core REST Principles, including Statelessness vs Stateful interactions, CORS errors, and the 6 REST Architectural Constraints with easy real-life shopkeeper analogies! In this video, I cover: ✅ What is Statelessness in REST APIs (Shopkeeper Analogy) ✅ Stateful vs Stateless Interaction — Core Differences ✅ The 6 Official REST Constraints (Client-Server, Statelessness, Cacheable, Uniform Interface, Layered System, Code-on-Demand) ✅ CSCULC Memory Trick to remember constraints for interviews ✅ CORS (Cross-Origin Resource Sharing) & How Browsers Block APIs ✅ Access-Control-Allow-Origin & Common CORS Headers 📄 Free easy-English PDF notes for this video are linked below — perfect for quick revision before interviews. 🎯 What's covered in this series: REST API Basics HTTP Methods & Status Codes Core REST Principles (this video) Security Basics Real-World API Design Performance & Caching Advanced Concepts 👉 Perfect for BCA / MERN stack students preparing for backend placements. 🔔 Subscribe and turn on notifications so you don't miss any video in this series. 💬 Comment your doubts — I reply to every comment. — 📂 Free PDF Notes: [https://github.com/Hardeep-cloud16/RE...] 📂 Full Playlist: [] 📂 Watch Video 2 (HTTP Methods): [] #RESTAPI #MERNStack #CORS #BackendDeveloper #WebDevelopment #CodingInterview #PlacementPreparation #JavaScript #NodeJS #ExpressJS #MongoDB #ReactJS #TechInterview #CodeWithHardeep #ComputerScience