H2O
The optimized HTTP1, HTTP2, and HTTP3 server
... mruby (Rack-based), graceful restart and self-upgrade, BPF-based tracing tool (experimental), and more. H2O is a new generation HTTP server. Not only is it very fast, it also provides much quicker response to end-users when compared to older generations of HTTP servers. Written in C and licensed under the MIT License, it can also be used as a library.