You can use a pure ruby resolver if you want. For example https://github.com/socketry/async-dns

But that way your sacrificing integration into your system's nsswitch which may want to do something completely different with your requests.

You could also query over dbus which can be async https://www.freedesktop.org/software/systemd/man/latest/org.... (if you can depend on systemd)

There is a few alternatives like getaddrinfo_a(3) but they have other downsides (fork safety concerns).

If you want more context, you can read: https://bugs.ruby-lang.org/issues/19430