Athenz is an open-source, fine-grained authorization and identity management platform designed for zero-trust environments. It provides centralized (ZMS) and decentralized (ZTS) services for issuing short-lived X.509 certificates, managing role-based access control (RBAC), and enforcing policies across multi-cloud and on-premise infrastructures. The system supports AWS, GCP, Azure, and Kubernetes workloads through pluggable attestation validators and credential providers, enabling service-to-service authentication and authorization without shared secrets. Architecturally, Athenz comprises three core servers: ZMS (management service for domains, roles, policies), ZTS (token service for certificates, OAuth2 tokens, SSH certs), and MSD (micro-segmentation for network policy management). A React/Next.js UI provides administrative management, while client libraries in Java, Go, and Node.js enable integration. The codebase is organized into modular Maven submodules with RDL-generated data models, extensive unit/integration tests, and Docker/Kubernetes deployment artifacts. Key patterns include factory-based dependency injection (e.g., cert signers, private key stores, notification services), dynamic configuration reloading, and composite validators for cloud attestation. This is a production-grade application with clean abstractions, well-defined interfaces, and significant test coverage. While the codebase contains some generated boilerplate and cloud-specific implementations that may drift, the core libraries and utility classes are reusable and demonstrate strong engineering practices.