In practice, it's probably not going to matter all that much because the average web service does way more time-expensive things like disk IO or SQL queries. The more significant effect is that async-await being really really fast enables you to use it in more places. For example, if you have a tight computation loop where different aspects of the logic are meshed together in a hard-to-read way, now you could try detangling it into several async actors talking to each other to make it more readable, without utterly destroying the performance characteristics.