> Modern I/O devices are highly concurrent and support massive throughput. A device can have millisecond latency while still executing an operation every micros

> Modern I/O devices are highly concurrent and support massive throughput. A device can have millisecond latency while still executing an operation every microsecond. In these cases, the operation latency doesn't matter, your thread has to handle events at the rate the device executes operations. This is true for some applications, like an OLAP database or similar. It’s not true for the typical user-facing app where you want to finish requests as soon as possible because a user is waiting and every millisecond costs you money.