Why the Same Bug Keeps Coming Back - And How to Stop It

A recurring bug in a multi-tenant SaaS application was caused by a missing line of code in some query handlers. The bug was fixed in one handler, but the same issue existed in three other handlers. The missing line, which added a null value to permitted warehouses, was necessary to include orders with no warehouse assigned. The bug was only visible in one handler, but affected users who had orders with no warehouse assigned. To prevent similar issues, the author recommends auditing code and testing for edge cases.