After writing about the cover flow for missed shifts, I kept thinking about one small moment that is easy to ignore: What happens if two people try to cover the same shift? On the screen, the flow looks simple. A shift needs cover. Available staff can see it. Someone taps “I can cover this.” The shift becomes covered. That is the clean version. But real products usually get messy in the small gap between someone tapping a button and the system deciding what actually happened. The UI can be fast, but it cannot decide the truth The tempting version is to make the UI feel instant. Someone taps the button, and the shift immediately looks like theirs. That feels nice. The product feels quick. The action feels clear. The user gets feedback right away. But there is a problem. The UI does not know if someone else tapped the same button at almost the same time. Maybe two staff members saw the available shift. Maybe both wanted it. Maybe both tapped within a few seconds of each other.…