> By definition, this order must be the top of the book, because it’s price already had to be aggressive, and there could be no other bids above us. Therefore,

> By definition, this order must be the top of the book, because it’s price already had to be aggressive, and there could be no other bids above us. Therefore, the new best bid increases from $99 to $102, since that is the limit price of our order. I really wonder here, in this part of "Introduction to Limit Orders", how they handle race conditions. Do you think they use a synchronous queue that queues orders while it's transacting, or do they try to also handle inserting orders during the process of filling orders?