Exposing your service via APIs

Microservices interact with each other and sometimes with the outside world over the network. A service exposes its capabilities through an API. I like to think of APIs as over-the-wire interfaces. Programming language interfaces use the syntax of the language they are written in (for example, Go's interface type). Modern network APIs also use some high-level representation. The foundation is UDP and TCP. However, microservices will typically expose their capabilities over web transports, such as HTTP (REST, GraphQL, SOAP), HTTP/2 (gRPC), or, in some cases, WebSockets. Some services may imitate other wire protocols, such as memcached, but this is useful in special situations. In 2019, there is really no reason to build your own custom protocol directly over TCP/UDP or use proprietary and language-specific protocols. Approaches such as Java RMI...