05. Regions

An AWS Region is a geographically separate portion of the AWS global infrastructure. Each region is separated from the others by hundreds of miles. They are isolated so that they are not interdependent, but they are connected by a global high speed, high bandwidth private AWS network.

Running in multiple regions is completely optional. In fact, if you don't intentionally try to, you'll only be running in one region. One reason for this is that there is some amount of additional cost to run in multiple regions. You must determine if your use case warrants the cost and complexity.

Most AWS services must be managed on a per-region basis. When you create a resource in one region, it does not exist in the other regions. There are a few exceptions, however. These exceptions are "global" AWS services such as IAM, where identity and access management must span the entirety of AWS or services such as CloudFront and S3 where they are not managed on a per-region basis.