Representational State Transfer (REST) APIs are all the rage. REST was defined by Roy Thomas Fielding in his PhD dissertation “Architectural Styles and the Design of Network-based Software Architectures". The architectural style of REST describes six constraints: Uniform interface Stateless Cacheable Client - Server communication Layered system Code on demand RESTful APIs typically use HTTP and HTTP verbs (GET, POST, PUT, DELETE, etc.) to send data to, or retrieve data from remote systems.