API architecture refers to a software building block that implements an API, providing a mechanism for invoking a task on another system. It consists of four primary responsibilities: interfacing, interpretation, computing, and data processing. The building blocks of an API architecture include the API interface block, which defines the specifications for the API; the API controller block, which controls the ingress and egress traffic; the API runtime block, which executes the business logic; and the API data bridge block, which orchestrates data access. Additional components of API architecture include API management, service mesh, security, and deployment considerations. API management involves administering the life cycle control of an API, while a service mesh connects multiple APIs to facilitate communication. Security is crucial to prevent macro-level threats, and deployment considerations involve choosing a hosting configuration that aligns with business goals. The goal of API architecture is to provide a robust framework for building modular and scalable systems.