Currently, Houdini uses Ruby 2.3 and the latest version of Rails 3.2. Ruby 2.3 is in security maintenance mode and will stop receiving security updates near the end of March, 2019. Accordingly we need to upgrade to Ruby 2.4 or higher. Additionally, as Rails 3.2 is not supported on Ruby 2.4 or higher, we need to update to at least Rails 4.2.