As far as I know, AWS removed data transfer costs over VPC peering connections on May 2021.
I see daily 400-500GB of data transfer which I assume most of them for the applications getting data via drivers. So the apps are on the same AWS region and VPC peering is enabled. Why I still see this cost?
Hi @Mete and welcome to MongoDB community forums!!
As mentioned in the AWS Documentation for VPC pairing, the no cost incurred is implemented when the two accounts (in your case is Atlas and AWS) are in the same availability zone.
Now even the Atlas cluster cluster is deployed in the region selected, the information about is the AZs(Availability Zone) is not provided.
Hence, in your case the AZs(Availability Zone) between the account A and the account B would be in different.
In case you have the paid support, you can reach out to MongoDB support where they can help you in identification for the information on AZ and the pricing in more details.
For further details, you can visit the Data Transfer documentation for deeper understanding.