I recently had an opportunity to help a developer with an ASP.NET Core app that was functionally correct but slow when under a heavy user load. We found a few different factors contributing to the app’s slowdown while investigating, but the majority of the issues were some variation of blocking threads that could have run in a non-blocking way. It was a good reminder for me just how crucial it is to use non-blocking patterns in multi-threaded scenarios like a web app.