Imagine you're responsible for a system with hundreds of microservices. You need to add critical features like logging, metrics, and security to all of them.

The thought of opening up every single codebase, adding new libraries, testing, and redeploying them is daunting.

What if there was a way to add these features without touching the application code?

This is the problem the Sidecar Pattern elegantly solves.

In this chapter, we will learn what the sidecar pattern is, how it works, when to use it, common use cases with real-world examples.

1. What Is the Sidecar Pattern?