WSO2 API Manager is an enterprise-grade platform for designing, publishing, managing, and monetizing APIs. In production, it operates as a distributed API management system comprising an API gateway, publisher portal, developer portal, key management server, traffic manager, and analytics engine. The architecture is modular: the `all-in-one-apim` profile bundles all components, while separate `control-plane`, `gateway`, and `traffic-manager` profiles support distributed deployments. Key entry points include REST APIs for publisher, store, admin, and governance functions, along with the gateway runtime that handles request routing, authentication (OAuth2, Basic Auth, mutual TLS), throttling, and mediation. Data flows involve API definition creation via publisher APIs, subscription management via store APIs, token generation by the key manager, and runtime request/response transformation by the gateway. External dependencies include databases (MySQL, DB2, etc.), identity providers (WSO2 IS, external), and message brokers for async event publishing. The codebase is a large Maven monorepo with extensive integration test suites (TestNG, Cucumber, Testcontainers) and a Python-based recommendation engine for API discovery.