There was mailing list discussion at the time journald was conceived though, you can find it if you look.
https://0pointer.de/blog/projects/the-journal.html might be a good entry-point.
It doesn't look like there was an open design review; Lennart Poettering just dropped it in in v38. https://lists.freedesktop.org/archives/systemd-devel/2012-Ja...
It seems a recurring (handling) issue but unfortunately it affects multiple linux distro defaults. This is the worse that can collaboratively happen for FOSS in general imho.
[1] Happened few times, I think RedHat as a whole even got banned from sending changes for a short while
> Performance: journal operations for appending and browsing should be fast in terms of complexity. O(log n) or better is highly advisable, in order to provide for organization-wide log monitoring with good performance
> Minimal Footprint: journal data files should be small in disk size, especially in the light that the amount of data generated might be substantially bigger than on classic syslog.