Application programming interface (API)

An Application Programming Interface (API) is a defined contract that specifies how software components communicate with each other—what requests can be made, how they must be formatted, and what responses will be returned. APIs abstract the internal implementation of a service, exposing only the functionality that external callers are permitted to use. In web and cloud contexts, REST, GraphQL, and gRPC are common API styles, with communication typically occurring over HTTP using structured data formats such as JSON.

APIs are the connective tissue of modern commerce technology stacks. E-commerce platforms, payment processors, logistics providers, ERP systems, AI services, and marketing tools all expose APIs that allow organizations to compose capabilities without building everything from scratch. In AI deployments, APIs are the mechanism through which applications access foundation models, vector databases, and AI-powered services. API design quality—stability, documentation, versioning, rate limiting, and security controls—directly affects integration cost and the long-term maintainability of commerce architectures. Organizations that treat API design as a first-class engineering concern reduce integration friction across their technology ecosystem.