Foundations of Scalable Systems

Chapter 9. Microservices

You don’t often see strong links between a mainstream software architectural style and an Italian-inspired, globally popular cuisine. This is, however, the case with microservices and pizza. The roots of microservices can be traced back to around 2008 when the approach was pioneered at scale by the internet giants we all know. At Amazon, the “two-pizza rule” emerged as a governing principle of team size for a single system component, which subsequently became known as a microservice. What is the two-pizza rule? Very simply, every internal team should be small enough that it can be fed with two pizzas.

It is a misconception, however, that microservices are in some sense smaller than a service. The defining characteristic of a microservice is their scope, organized around a business capability. Put very simply, microservices are an approach to designing and deploying fine-grained, highly cohesive, and loosely coupled services that are composed to fulfill the system’s requirements. These fine-grained services, or microservices, are independently deployed and must communicate and coordinate when necessary to handle individual system requests. Hence, by their very nature, microservices architectures are distributed systems, and must deal with the various scalability, performance, and availability issues I have described in previous chapters.

Microservices are a popular, modern architectural style with plenty of engineering advantages in the right context. For ...