Open Policy Agent
Open Policy Agent (OPA) is an open-source, general-purpose policy engine that enables unified, context-aware policy enforcement across the entire stack. It decouples policy decision-making from application logic by using a high-level declarative language called Rego, allowing policies to be defined, managed, and evaluated consistently in environments like Kubernetes, microservices, CI/CD pipelines, and more. OPA provides a lightweight service that can be deployed as a sidecar, host-level daemon, or library to enforce policies for authorization, admission control, data filtering, and configuration validation.
Developers should learn and use OPA when they need to implement fine-grained, scalable policy enforcement in cloud-native applications, especially in Kubernetes for admission control (e.g., validating pod configurations) or in microservices for authorization (e.g., API gateways). It's valuable in DevOps and security contexts to ensure compliance, reduce human error, and centralize policy management across diverse systems, as it integrates with tools like Kubernetes, Terraform, and Envoy. Use cases include enforcing security policies, resource quotas, and organizational standards without hardcoding rules into applications.