This isn't for a banking system, this is for building collaborative apps. If you press "A" and your friend press "B" into a Google Docs document at the same tim

This isn't for a banking system, this is for building collaborative apps. If you press "A" and your friend press "B" into a Google Docs document at the same time, you also don't know if the document is going to read "AB" or "BA". In practice, this is not an issue.