Discussing performance only makes sense in the context of a particular awk implementation, like TFA is doing as well. If you‘re (stuck) on gawk, try setting LANG=C to prevent Unicode/multi-byte regexp execution, or switch to mawk (which according to [1] is much faster than cpython).

[1]: https://brenocon.com/blog/2009/09/dont-mawk-awk-the-fastest-...