@mdbraber @stux not sure if you were able to get stuff up and running again (not on an instance you control), but double checked with a book Sidekiq in Practice I recently read: thing with threading in ruby is that these do not really work in parallel. There is a GVL; if it is performing some IO task, however, it can release the lock and allow another thread to work. Hence it is better to have more than use more than one thread. But too many will probably block DB connections / IO pools, and push memory consumption over limits.

See also this post by the author of the aforementioned book, @nateberkopec https://www.speedshop.co/2020/05/11/the-ruby-gvl-and-scaling.html