One of the first major bugs I hit as a junior developer looked simple at first. My React frontend refused to talk to my Express backend. The terminal kept throwing errors, the browser showed failed requests, and after a few hours I was convinced I had fundamentally misunderstood how APIs worked. At first, I did what I think a lot of beginners do: randomly changed things until something worked. Bad idea. Eventually I stopped, took a breath, and approached it the same way I used to approach problems in scientific environments: isolate variables and identify root causes. I started using a simple “5 Whys” approach. Problem: Frontend couldn’t connect to backend. Why? → The request was failing. Why? → The API endpoint returned a CORS error. Why? → Express wasn’t configured to allow requests from the Vite frontend. Why? → I never added CORS middleware. Why? → I didn’t fully understand how frontend/backend communication actually worked yet. That single debugging session changed how I think about development.…