How to diagnose a slowdown?

80% doesn’t sound problematic to me.

More interesting is that you have a lot of sidekiq processes and yet I see the annotation “0 of 5 busy” - you have more than 5. You also seem to have a lot of unicorn threads.

I suggest a new topic here, with your htop output, including your yml config as to whether you’ve adjusted your unicorn count. Ask whether this set of processes looks reasonable.