Used to work for one of the big ones IMO the reason they don't do this is because you would have to design every system with billing as a critical path depende

Used to work for one of the big ones IMO the reason they don't do this is because you would have to design every system with billing as a critical path dependency For example say you have a service that lets people run batch jobs What happens if the pre-pay credit of the account runs out mid way through the job? Does your job service have to constantly check the remaining balance as its running and abort halfway through? What happens if the account balance service goes down? Or would you somehow reserve the credit before the job starts? Well in that case how do you know how long the job will run? Its possible to do in theory but it would be a pain to support