Unhandled Promise Rejections: The Tiny Mistake That Crashed Our Node.js App

Imagine deploying a Node.js backend service that works flawlessly in development, only to have it mysteriously crash in production. Everything ran fine on your laptop, but on the live server, the process keeps shutting down unexpectedly. In our case, the culprit was a single unhandled promise rejection — one missing .catch() in our code caused Node to exit abruptly whenever an error occurred. That one “tiny” mistake made the difference between a stable service and frequent downtime. In this article, we’ll explore how a misconfigured error handling in a Node/Express API can bring down an application, and how to diagnose and fix it to prevent future crashes.