For those interested, this is a pretty good Mastodon server setup:
1) hardware box w/32 cores, 32gb, 1TB SSD, 1Gb eth, Ubuntu 20.04,
2) 8x Puma, 1xPgsql (pgtuned), 1xRedis (500mb, no save),
3) Sidekiq in 4 procs, 25 threads/db-conn, with pull, ingress, and default each with a dedicated process.
I think this is going to scale quite well; can add more sidekiq procs. And then will break out to multiple boxes. But lots of dedicated CPU is the key bottleneck. This slaughters the queue.