DataCenters

An AWS region e.g. us-east-1 has physical data centers where the actual infrastructure lives, e.g. us-east-1a, us-east-1b, etc.

But there's something you may not have known:

Availability Zones (AZs) in an AWS account may not always refer to the same data center(s) in a different AWS account.

In other words, for a region us-east-1, the AZ us-east-1a in one person's account (Account A) may not be in the same data center as the AZ us-east-1a in another person's account (Account B).

To ensure that resources provisioned in different AWS Accounts are placed in the same physical location, using the AZ name is not a reliable option.

Why Should You Care?

1. Latency: In a multi-account environment, where you have different AWS accounts for different purposes, you may require a service in one account to connect with another service in a different account. By placing those services in the same physical data center, the number of hops is reduced.

2. Compliance: In other to comply with company or national policies, some services may be required to stay in a particular location. Placing those services in the same region is a great way to ensure compliance, and you can go further to ensure that they are in the same physical data center.

If you care, then there is a solution -- Zone IDs!

Availability Zone ID

An Availability Zone ID is an ID that is consistent across all AWS accounts. An AZ Zone ID in Account A is the same physical data center for the same Zone ID in Account B.

• AZ Zone Name is not necessarily the same physical location in different AWS Accounts
• AZ Zone ID is the same physical location in different AWS Accounts

To get the availability zone ID, you can use the following command:

aws ec2 describe-availability-zones --region us-east-1

You can now proceed to use the Zone ID reliably.

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