OPA is an open source, general purpose policy engine that allows developers to use policy-as-code to enforce authorization across the cloud-native stack. To accomplish this, OPA decouples policy decision making from applications, allowing for uniform policy and increased application performance. Thanks to its declarative language policy language, Rego, OPA can make decisions for Kubernetes, Microservices, functional application authorization, gateways and more. It structures these policies based upon hierarchical structured data, such as JSON or YAML data, with several use cases of integrations.