Why composite services?

In microservices architecture, the implementation of the service definition is done by smaller deployable units instead of large monolith applications that run in application servers. This makes the services easier to write, faster to change and test, and quicker to deploy. But this also creates a challenge for microflows that span two or more microservices, perhaps across multiple bounded contexts. In a monolith application, such microflows could be coordinated as a single transaction across two modules deployed in a single deployable unit. In microservices architecture, distributed transactions are discouraged and hence, microflows have to be solved using a composition approach.