Service consumers either use client-side discovery or the server-side discovery to locate the actual running microservice instance. They eventually get the location of a service from the service registry.

Service registry is a datastore of microservices that records their instances and locations.

An instance of a microservice is responsible for registering itself with the service registry. It registers itself with the service registry on startup, and makes itself available for discovery. On shutdown, the service instance unregisters itself from the service registry. There is a mechanism that enables the service instance to keep updating the registry at periodic intervals in order to validate its existence.