Package serving
Packagecloud serves incoming client connections from package manages (like yum, apt-get, npm, gem, pip, maven, etc) as well as requests to the website's UI using a set of processes called "Unicorn processes". The number of unicorn processes dictates how many concurrent connections can be handled. Keep in mind that typically these requests complete very quickly (in under 100ms), and the NGINX webserver will wait for a connection if all the unicorn processes are active.
In order to adjust the number of Unicorn processes, you should modify your /etc/packagecloud/packagecloud.rb file and modify the unicorn['worker_processes'] setting. This setting is defaulted to the number of CPUs on your system + 1. We recommend choosing this value carefully; creating many more processes than CPUs on your system will not result in additional concurrency.