You are building a matching engine. What exact data structures would you use to store a limit order book so that you can get the best bid/ask fast, but also cancel a specific order in O(1) time?

你正在搭建一个撮合引擎。你会用哪些具体的数据结构来存储限价指令簿（LOB），既能快速获取最优买卖价，又能做到在O(1)时间内撤单？