an ASP.NET performance bottleneck mystery

Question

A classic ASP.NET app - AppSrv + MS SQL DB. Both servers are heavy-lifters 8 cores, 20 GB of RAM. When load testing, the throughput goes somewhere to 400 VirtualUsers (according

Answer 1

Add logging to your app with some appropriate unique request ID so you can effectively trace how long each operation within a page load takes. For instance, logging before and after every database call will show whether the database calls are taking a long time or not.

As others have suggested, adding logging/profiling on the database side will show whether that's deadlocked (or similar).