Increased SAE1-DataTransfer-OutByes cost after upgrading to SDK v3 in Nodejs

Hi everyone!

A few days ago, I noticed a spike in our bill, so I checked what happened. I saw that our S3 costs went up by about 100% compared to the previous month. I started investigating and discovered that SAE1-DataTransfer-OutBytes doubled. After further research, I found that the exact day the cost doubled was when we updated the Node.js SDK to version 3.

This is a fairly small and simple system that uses S3 to store some pictures. These pictures are then visualized on a dashboard and can be downloaded using S3 links directly. All of this works in a single region (sa-east-1) and is part of a VPC containing an ECS cluster with about 4-5 instances.

I configured an S3 endpoint for the VPC to reduce data transfer costs, and using tracert inside the instance seems to be working correctly. I can't find a reason why updating the SDK version could have increased the cost by this much. This is how the graph looks for April (we updated the SDK on the 22nd):

The red bit represents the usage type SAE1-DataTransfer-OutBytes. At first, I thought it might be a security issue, but the usage has remained consistent since that day, as you can see here in the May graph, which makes me think something in the new SDK causes the data transfer to increase?

Any ideas of what can be causing this issue? I'm a bit lost here.

Thanks!