Introduction

Most business applications are composed of two main parts:

• The application binary
• A configuration

A simple example is a web server, such as NGINX or httpd (Apache). Neither are very useful without a configuration. However, when you combine the application with a configuration, it becomes extremely useful.

In the past, we coupled the application and the configuration into a single easy-to-deploy unit. As we moved into the early days of cloud-native microservices applications, we brought this model with us. However, it’s an anti-pattern in the cloud-native world. Cloud-native microservices applications should decouple the application and the configuration, bringing benefits such as:

• Reusable application images
• Simpler testing
• Simpler and fewer disruptive changes

We’ll explain all of these, and more, as we go through the chapter.