Reactive Microsystems

Introduction

The Evolution of Scalable Microservices

In this report, I will discuss strategies and techniques for building scalable and resilient microservices, working our way through the evolution of a microservices-based system.

Beginning with a monolithic application, we will refactor it, briefly land at the antipattern of single instance—not scalable or resilient—microliths (micro monoliths), before quickly moving on, and step by step work our way toward scalable and resilient microservices (microsystems).

Along the way, we will look at techniques from reactive systems, reactive programming, event-driven programming, events-first domain-driven design, event sourcing, command query responsibility segregation, and more.

We Can’t Make the Horse Faster

If I had asked people what they wanted, they would have said faster horses.

Henry Ford¹

Today’s applications are deployed to everything from mobile devices to cloud-based clusters running thousands of multicore processors. Users have come to expect millisecond response times (latency) and close to 100 percent uptime. And, by “user,” I mean both humans and machines. Traditional architectures, tools, and products as such simply won’t cut it anymore. We need new solutions that are as different from monolithic systems as cars are from horses.

Figure P-1 sums up some of the changes that we have been through over the past 10 to ...