A cartridge is a container for a framework, load balancer or data management system. You can add a cartridge in a platform as a service (PaaS) for scalability. In Stratos, cartridge runtimes create service runtimes. For example, if you want to have a PHP runtime, you can use a PHP cartridge to get the runtime to deploy your PHP application. A cartridge can be fully configured with all the software and configurations, or zero configured where the cartridge user can install and configure what they want. For more information on all the properties that you can define in a cartridge definition JSON, see the Cartridge Resource Definition.