Overview
Recently, AWS identified an issue with intra-regional data transfer metering when using the cross zone Network Load Balancer (NLB) feature, which resulted in AWS under-charging for data transfer usage when using the cross zone NLB feature. MongoDB Atlas deploys cross-zone NLBs for our private endpoint service (AWS PrivateLink).
This issue specifically impacts the use of the cross-zone Network Load Balancer (NLB) feature when the NLB and the target are in different availability zones (AZ). AWS intends for data sent between the NLB (AZ 1) and the target (AZ 2) to incur data transfer (DT) charges. This is charged at $0.01/GB for ingress and egress data at both the source and the destination. Due to a previous under-metering issue, AWS has not been charging for DT on the NLB (where applicable). Specifically, AWS had been correctly charging for DT on the target. However, the NLB portion of the DTAZ was not being charged. After AWS fixes the issue, AWS will begin charging for DT as intended.
AWS will begin correctly billing for this usage from May 1, 2025. This update may result in a change to your Atlas bill. This is because MongoDB passes through cloud provider data transfer costs. AWS has stated that they will not retroactively charge for the underbilled usage.
In line with MongoDB's commitment to customers, MongoDB will cover these extra costs through May 15, 2025. Based on analyses with AWS, the estimated change will result in an average increase of 1.0% to monthly Atlas bills from May 15, 2025 onwards.
How does this impact my MongoDB Atlas bill?
Starting May 15, 2025, you may notice a slight increase on your Atlas organizations's monthly invoices. This reflects corrected charges for AWS NLB data transfer.
This estimate is based on usage from February 2025. The actual increase may vary depending on actual data transferred.
These charges will be included in invoices as part of the existing "Atlas AWS Data Transfer (Same Region)" SKU line item. Therefore, you can expect the charges for this line item to increase.
MongoDB recommends reviewing this document on best practices to optimize and reduce data transfer cost. In many cases, taking advantage of things like enabling network compression can reduce the amount of data transferred.
For billing-related questions, open a case with MongoDB Support. For assistance in optimizing your configuration, contact your account team.