Add the following to /etc/rsyslog.conf after '$ModLoad imuxsock' and '$ModLoad imjournal':

$IMUXSockRateLimitInterval 0
$IMJournalRatelimitInterval 0

Set the following in /etc/systemd/journald.conf:

Storage=volatile
Compress=no
RateLimitInterval=0
MaxRetentionSec=5s

Restart journald and rsyslog to pickup the changes with:

systemctl restart systemd-journald.service
systemctl restart rsyslog.service