Business functionality in a microservice architecture is distributed over multiple microservices, so one request from a client can internally fans out to many separate requests and it is highly probable that one of the services is slow or down. But as a developer, we need to know how to track which service is slow in the microservices web, so somehow we need to group the requests logically. It is always a good practice to generate a random “unique correlation id” for a client request and pass that “unique correlation ID” to every internal request so in a log it can be tracked by that Id and find the call trace accordingly.