Nether lags dedicated servers

Can you provide a copy of an affected world?

I personally cannot as I am not the owner of these servers, I admin one but the rest of the information has come from other users using different hosts and it's the same results, even loaded up a brand new world and going in causes this 

Would BDS-19101 describe your issue?

The CPU only got as high as 17% and immediately dropped down to around 3% after loading the nether.

When entering the nether it lags the entire server including the overworld dimension and continues to lag until the user(s) leave the nether dimension, after they leave the lag is gone and everything goes back to normal, have also noticed when moving around in the nether chunks take awhile to load they're just giant areas of emptiness until they do load 

Our server is suffering from the same issue, as well as BDS-19101.  Going through a portal can takes minutes to happen and the CPU usage spikes to 100% throughout that time.  However once the nether eventually loads for the player CPU usage drops back to standard levels, however the world in all 3 dimensions is incredibly laggy.  eating can take 4-5 attempts, blocks break and place eratically, and so on6

Same issue on bedrock server as of today. This doesn’t happen on realms so there is an obvious fix someone knows.

I have this problem too. Server lags really bad for even one person when entering the nether and chunks can take a long time to load. I have Ryzen 5 5800x and 32GB RAM that just runs BDS.

I tested this issue in the local game. When players are in the Nether, entering the map takes significantly longer, and the CPU usage remains consistently above 90%.

My friend with an Ultra 9 takes over 20 seconds to load the map, while most players experience a 7-8 second delay. On the Dimensity 9300, loading takes over 30 seconds, whereas entering the Overworld only takes a few seconds.

I have the same problem on the realms I join. Very annoying.

this is fixed in 1.21.100 for me