TLDR: account balance is not a good example to simply explain actors. Actor model in general doesn't guarantee the ordering of the messages. The is possibilit

TLDR: account balance is not a good example to simply explain actors. Actor model in general doesn't guarantee the ordering of the messages. The is possibility that all the withdraw messages arrive first and all the deposits later. Balance poll result makes sense only with assumption "all messages before this point of time have been processed"