# Container-based application design
<a name="application-design"></a>

## Java EE replatforming challenges
<a name="replatforming-challenges"></a>

You can face the following challenges when you migrate your Java EE application to a containerized platform in the AWS Cloud:
+ **Disposability** – To keep a container "stateless," you might have to store session state in an external database. Container-based applications require a faster, smaller application runtime, and your Java EE application server might not be able to run in the container environment. 
+ **Container platform compatibility** – You might have to reduce application runtime-specific capabilities, such as clustering, application deployment, and memory replications. 
+ **Portability** – Container-based applications are deployed by using an application runtime, while traditional Java EE applications are deployed by using application packages (.jar or .war files).

## Best practices for container-based application design
<a name="best-practices"></a>

We recommend that you follow these best practices when you design your container-based Java EE applications for the AWS Cloud:
+ Avoid making changes to your container instance after you created it. If you must make changes, build a new container image and reuse that new image across all environments.
+ Avoid storing permanent data inside your container.
+ Design your container so that it addresses a single purpose.
+ Make sure that your container implements all necessary APIs.
+ Design your container so that its system requirements are built around CPU usage, system memory, and persistent storage. 

For more information on best practices, see [Principles of Container-based Application Design](https://kubernetes.io/blog/2018/03/principles-of-container-app-design/) in the Kubernetes documentation.