If you have DB access, the values are in the local_site_rate_limit table. You’ll probably have to restart Lemmy’s API container to pick up any changes if you edit the values in the DB.

100 per second is what I had in my configuration, but you may bump that up to 250 or more if your instance is larger.

Fixed:

UPDATE local_site_rate_limit SET message = 999, message_per_second = 999 WHERE local_site_id = 1;