Here's the oversell bug that bothers me most. A customer support ticket says two people were promised the last unit of the same product. You open the database and look at the stock row: OnHand = 1 , Reserved = 1 , Available = 0 . Perfectly consistent. No negative number, no constraint violation, no exception in the logs. Everything looks right, and you still sold one unit twice. In this post I'll focus on that one part of the problem: why the stock row looks healthy after an oversell, whic...