> For the complete documentation index, see [llms.txt](https://abdulrahman-1.gitbook.io/my-digital-garden/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://abdulrahman-1.gitbook.io/my-digital-garden/level-2-system-design/step-4-low-level-detailed-design-system/application-servers.md).

# Application Servers

## Stateless App server

* All servers don’t remember client sessions
  * Using server-side cache like Redis
  * Using self contained data coming with the request such as tokens payload, headers, request payload...

> ## Stateful App Server
>
> * Remember user sessions
>   * Hash table (or any other cache data structure) to remember which app server to routes to
>   * Sticky sessions
>   * More difficult to scale

## REST APIs

{% embed url="<https://restfulapi.net/>" %}

{% embed url="<https://docs.microsoft.com/en-us/azure/architecture/best-practices/api-design>" %}

{% embed url="<https://hackernoon.com/restful-api-designing-guidelines-the-best-practices-60e1d954e7c9#comment-4865610272>" %}

{% embed url="<https://blog.restcase.com/rest-api-error-codes-101/>" %}