Scalability of speech is a common approach; see The Scale Cube which is discussed in the book The Art of Scalability from Martin L. Abbott and Michael T. Fisher. The concepts of the Scale Cube are fully applicable to microservices, and web applications in general, that need to be scalable:

The concept of a scale cube shows that there are basically three forms of scalability: x-axis, y-axis, and z-axis. To better understand each of these three approaches, we will use some diagrams.