There is some debate regarding whether microservices are a part of SOA or not. Most of the time, the term SOA is pretty much equivalent to the ESB design. Microservices are in many respects the opposite of ESB. This leads to opinions that microservices are a distinct pattern from SOA, being the next step in the evolution of software architecture.
We believe that they are, in fact, a modern approach to SOA that aims to eliminate some of the problems featured in ESB. After all, microservices fit within the definition of Service-Oriented Architecture very well.
Microservices are the subject of the next chapter.