Syscalls have gotten quite a lot slower after Specter/Meltdown mitigations. Though I suspect that if you're writing a web service that wants TPC you should just disable these - I've told that to Scylla Cloud before, they have no reason to keep them enabled and plenty of reasons to disable them.

The other thing is 'io_uring', which is trying to come at the problem by removing context switching altogether by providing a cheap primitive for communicating with the kernel.

Sadly io_uring has its share of vulnerabilities as well

Of course, I'm very aware of that fact. But it is designed to minimize system calls exactly because they can add significant overhead.