I switched out asio's epoll backend for its io_uring in a database server and CPU utilization shot up. Probably depends on usage and the specifics of how it's integrated into the event code.

Boost is so inconvenient, they're huge dynamic libraries that are a pain to build and use. Even when I was already using CMake, getting Boost installed in a way where it could be discovered was super annoying. (I was on Mac, though)