It’s every developer's favorite Friday afternoon nightmare:

A user complains that a feature in the app is hanging. You take the exact SQL query executed by the application, paste it into SQL Server Management Studio (SSMS), hit Execute... and it finishes in 0.02 seconds.

You run it again. Blazing fast.

Yet, inside the application, it continues to time out.

If you’ve been building database-backed apps long enough, you’ve almost certainly run into Parameter Sniffing.