Gitaly provides high-level RPC access to Git repositories. It is used by GitLab to read and write Git data.

Handles slow HTTP requests for GitLab

Multithreaded web server for Ruby on Rails.

Sidekiq is an open source job scheduler written in Ruby. It's important to be aware that Sidekiq by default doesn't do scheduling, it only executes jobs. The Enterprise version comes with scheduling out of the box.