Chapter 9
Interconnect

In the previous chapter, we looked at instances running on machines. But really, who is interested in a single instance running by itself? A standalone process might as well be on a desert island. We need to connect them together into a system. This chapter continues our iterative zoom-out to look at how the instances work together and find each other, as well as how callers invoke them. It’s time to look at the “interconnect” layer from our schematic (shown in the following figure).

The interconnect layer covers all the mechanisms that knit a bunch of instances together into a cohesive system. That includes traffic management, load balancing, and discovery. The interconnect layer is where we can really create high availability. As with the instance level, we also need to create transparency and control. None of it happens by accident.