One of my mods, forgery, adds about 8k commands as recognized by serverutils - enough to configure the mod entirely.
Since adding this mod to the server, there is a huge ~20 second lag spike whenever a player connects, switches dimensions or respawns. Spark analysis shows the server is spending a long time filtering then reapplying all permissions to the player, and spark's GC monitor showed over 800mb/s being freed during this time.

I'm not sure if this lag applies equally to ops and default rank players. I suppose the commands have to be filtered either way, but the spike seemed much smaller when some unranked players did these actions. However removing op rank (and vanilla status) from myself doesn't reduce the issue. Maybe something else eg. latency exacerbates it? Or something's cached poorly? Can't say, but I can provide the info I do have:

https://cdn.discordapp.com/attachments/622089187809820672/1064550148098760764/Permissions.json
https://spark.lucko.me/7sOxwVHrG6

Using server_utils-1.16.5-2.8.0

Update: the lag persisted for me because i had the * permission applied to myself as well as the op rank. I think this issue relates to actually applying permissions to players, and default rank players lag the server less in this situation. The problem is not fixed, ops still lag the server.