The bug wasn’t performance. It was silence. I ran into this while building a Next.js dashboard. There was a button that triggered a report generation flow. Some client-side processing, then an API call. Lighthouse looked great. API response was around 80ms. But session recordings told a different story. Users were clicking the button 3 to 5 times in a row. No errors in logs. No failed requests. Everything technically worked. So I watched one of the recordings more carefully. The moment the user clicked, nothing changed on screen. No loading state. No disabled button. No visual feedback at all. The UI looked exactly the same before and after the click. That was the issue. 80ms response, zero perceived response The backend was fast. The interface just didn’t acknowledge the interaction. From the user’s point of view, the click didn’t go through. So they clicked again. And again. Not because they were impatient. Because the UI stayed silent.…