High CPU usage (Ruby)

Product Support
9

Take a look at discourse-setup, which handles the scaling for new installs today:

# UNICORN_WORKERS: 2 * GB for 2GB or less, or 2 * CPU, max 8
  if [ "$avail_gb" -le "2" ]
  then
    unicorn_workers=$(( 2 * $avail_gb ))
  else
    unicorn_workers=$(( 2 * $avail_cores ))
  fi
  unicorn_workers=$(( unicorn_workers < 8 ? unicorn_workers : 8 ))

That second statement, using double the number of available cores, is the default on systems with more than 2GB RAM. It looks as though your issue is more down to a tug-of-war between your instances (host resources), rather than a discourse problem.