Ok, let's just go ahead and get this one out of the way. Let's start this book off by talking a bit about exactly what a microservice is, to us at least. Let's start with a simplistic visual diagram of what we're going to accomplish in this book. This diagram says it all, and if this looks too confusing, this might be a good place to stop reading!

Let's next agree to define a microservice as an independently deployable and developable, small, modular service that addresses a specific and unique business process or problem, and communicates via a lightweight event-based, asynchronous, message-based architecture. A lot of words in that one I know, but I promise by this end of the book that the approach will make perfect sense to you. Basically, what we are talking about here is the Messages central component in the previous diagram.

I know that some of you might be asking yourselves, what's the difference between a service and a microservice? That is one very good question. Lord knows I've had some very heated discussions from non-believers over the years, and no doubt you might as well. So, let's talk a bit about what a Service-Oriented Architecture (SOA) is.