I guess you are doing something very wrong if you have such performance trouble all the time.

The Pi (up to 4) is known for bad disk I/O. Look into this area first.

I am running my nc on a weak old low power deskop CPU (and with real SATA harddisks) and only when I ask for long running jobs (like, create the previews and icons for 200 new photos) I can watch any slow responses at all.