“In less than 1h, we’ve created 474 new subscriptions for a total of $73,271.36.”
A minor Mongoid release changed what or() means. One query went from “this user AND unlocked” to “this user OR anyone unlocked,” and the billing code renewed customers who had canceled long ago. A minor version changed the meaning of a database query. Semantic versioning is a promise nobody enforces, and the Friday deploy found out.