I've often ended up reimplementing what I need because the API from the famous libraries aren't efficient. In general I'd love to send a million of requests all in the same packet and get the replies. No need to wait for the first reply to send the 2nd request and so on. They can all be on the same TCP packet but I have never met a library that lets me do that.
So for example while http3 should be more efficient and faster, since no library I've tried let me do this, I ended up using HTTP1.1 as usual and being faster as a result.