AZs – Introduction to AWS Security Concepts and the Shared Responsibility Model

AZs

Every region is composed of multiple isolated sites, referred to as AZs. Each AZ houses one or more data centers, all of which are equipped with redundant power, networking, and cooling facilities. These AZs are strategically placed at a considerable distance from each other, spanning several kilometers, but are still within 100 kilometers (60 miles) proximity.

AZs offer a way to build applications that are resilient to individual data center failures, a key consideration for security and business continuity. By distributing instances across multiple AZs within a region, you can protect your applications from the failure of a single location.

However, It is important to note that the selection of AZs should not be done randomly or excessively. While AWS does provide high availability through multiple AZs, the architecture of your application is under your responsibility and plays a crucial role in determining its resilience. For example, if different components of your application stack are spread across different AZs without proper planning, it can create more points of failure rather than improving the overall availability of the stack. When architecting your application, it is advisable to consider the interdependencies of your application components and aim to minimize the impact of a single AZ failure on your overall application. This might involve replicating critical components across multiple AZs or designing your application to degrade gracefully in the event of a component failure.

Furthermore, the level of built-in resiliency can vary depending on the AWS service you choose. For instance, more managed services, such as Lambda, provide multi-AZ resilience out of the box, reducing the need for manual configuration. On the other hand, services such as RDS for MySQL or EC2 require more manual configuration and additional costs to achieve a similar level of resilience.

Understanding these factors can help you make informed decisions when selecting and configuring AZs, ultimately improving the security and resilience of your applications running in the AWS cloud.