Sidekiq processes?

I’m running a GitLab instance for my personal projects on a RPi, now i’m looking forward to lower resource usage, disabled some services, and decreased the sidekiq concurrency (to 9 as of now), thing is htop shows about 15 sidekiq processes running and saying [0 of 9 busy] (all of them, of course, with different pid).

is this normal? sometimes it gets too slow to access through web UI. I’m using an external HDD as root filesystem and a 4GB swap partition.