onsite:1. 给一堆users，和她们的上下车的时间，然后给出所有的乘车数目变化的时间点，扩展是有可能同一个user id，应该不同的人打开了app，乘车. 所以时间有overlap，如何handle
2. long polling, push, user based, geograph based and mixed hashing, pros and cons, if a rider is assigned a driver, and the server really got the ack, why the rider does not know he is assigned.... 这个问题最后回到的是rate limiting,要求写一个Mt 的rate limiter
,用circular buffer
3. behavior +turing code related brain storming
4. hiring mgr, project and behavior
5. Design a feature that the riders can share the trip with the followers