Something You Didn't Know About AWS Availability Zones

#devops #aws #cloudcomputing

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?

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.
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