## PART III Structural Patterns 

Container images and containers are similar to classes and objects in the object- oriented world. Container images are the blueprint from which containers are instan‐ tiated. But these containers do not run in isolation; they run in other abstractions such as Pods, which provide unique runtime capabilities. 

The patterns in this category are focused on structuring and organizing containers in a Pod to satisfy different use cases. The forces that affect containers in Pods result in the patterns discussed in the following chapters: 

• Chapter 14, Init Container , introduces a separate lifecycle for initialization-related tasks and the main application containers. 

• Chapter 15, Sidecar , describes how to extend and enhance the functionality of a pre-existing container without changing it. 

• Chapter 16, Adapter , takes an heterogeneous system and makes it conform to a consistent unified interface that can be consumed by the outside world. 

• Chapter 17, Ambassador , describes a proxy that decouples access to external services. 

