VPC interface endpoint selection

Question

if you place an interface endpoint in multiple AZ's but there is only one consumer from single AZ, what happens by default, does traffic round robin between both AZ's causing cross AZ traffic?

Related to this, when creating a VPC should both DNS resolution and Hostnames be enabled and in the VPC endpoint creation should "Enable Private DNS name" be enabled?

What happens if for instance only VPC DNS resolution is enabled (which I think is default), does traffic still go PrivateLink?

Accepted Answer

Correct. It uses either ENI which could incur cross-AZ cost.

Answer

It depends on whether you use regional or zonal specific host name of the endpoint. Please refer to the following:
https://docs.aws.amazon.com/whitepapers/latest/aws-privatelink/creating-highly-available-endpoint-services.html
https://repost.aws/questions/QUOus1wYtCS6O4IBhCYAdSoA/data-routing-to-vpc-endpoint-from-different-az

VPC interface endpoint selection

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