We configured our production Beaker instance to use createrepo_c instead of createrepo a long time ago, for its much better speed and lower memory usage (bug 1002395). However the default in Beaker is still createrepo, not createrepo_c. It's been running well since then (aside from one early bug: https://github.com/rpm-software-management/createrepo_c/issues/3).
We should switch the default to createrepo_c (and also update the Requires for it).
This bug fix is included in beaker-server-24.0-0.git.123.c4a89ef which is currently available for download here:
Beaker 24.0 has been released.