At my local Costco, they sell this movie ticket bundle voucher: 2 general admissions, 2 soft drinks, and a popcorn.
I bought one. Planning to enter the cinema for the first time in years to watch Blades of the Guardians.
I used the cinemas ticket booking mobile app, entered the code, picked our seat, and pressed the button to complete the transaction.
App errored out.
I tried again but now the system marked my voucher as used.
So... the dev forgot to wrap things in db transaction?? ๐๐๐