describeInstanceTopology

Describes a tree-based hierarchy that represents the physical host placement of your EC2 instances within an Availability Zone or Local Zone. You can use this information to determine the relative proximity of your EC2 instances within the Amazon Web Services network to support your tightly coupled workloads.

Instance topology is supported for specific instance types only. For more information, see Prerequisites for Amazon EC2 instance topology in the Amazon EC2 User Guide.

The Amazon EC2 API follows an eventual consistency model due to the distributed nature of the system supporting it. As a result, when you call the DescribeInstanceTopology API command immediately after launching instances, the response might return a null value for capacityBlockId because the data might not have fully propagated across all subsystems. For more information, see Eventual consistency in the Amazon EC2 API in the Amazon EC2 Developer Guide.

For more information, see Amazon EC2 instance topology in the Amazon EC2 User Guide.