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See The Cornell “Standard” AWS VPC.
Can I coordinate VPC Availability Zones
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between AWS accounts?
While it may seem like a useful configuration to coordinate your "Availability Zone A" resources with another AWS account's "Availability Zone A"In practice, no. To ensure distribution of load across their infrastructure, AWS creates an independent mapping of Availability Zone designations (ie: "us-east-1a", "us-east-1d") for each account. Within the same Region, there is no way to guarantee you are both referencing the same Availability Zone in an AWS Region. According to the that you see as "zone A" lives in the same back-end environment as "zone A" seen from a different AWS account. For more information, see the AWS documentation on Regions and Availability Zones, there is a unique mapping of Availability Zone letter designations for each AWS account to ensure distribution of load across their infrastructure.