The rapid growth of io_uring

In my understanding, you can still use epoll together with io_uring. For example, use IORING_OP_POLL_ADD to register epoll id to io_uring, this occupies only 1 slot.

Once epoll is ready, add all the ready descriptors to io_uring (readv / writev etc.) in batch. These descriptors will be dealt with immediately because they are in ready state.

Even you have say million connections (and most of them are idle), it is still possible to deal with them without issues.

You at least save some syscalls due to the batch operations, and for the application side, it is still more asynchronous than calling readv/writev yourself.