From where data transfer going to be performed

Hi,

The S3 data transfer happens from the region the S3 bucket is at. Even though S3 appears as a Global service in the Console it's not. So if you go to the S3 Console you will see in the list a column with the S3 bucket region.

I probably need some more details on your specific use case but it seems most of the charges are from regional data transfer that means you probably created the S3 in a different region than where you're running your services.

Hi

Cost Usage Reports are a great way to understand your S3 costs. You should go through following link which details billing for S3. https://docs.aws.amazon.com/AmazonS3/latest/userguide/BucketBilling.html In particular refer the section for usage reporting https://docs.aws.amazon.com/AmazonS3/latest/userguide/aws-usage-report-understand.html Your bill & cost usage reports will provide the breakdown of the costs. The metrics will show whether the data transfer costs is from data going to internet or others.

As always leverage tags for your buckets so you can identify and map the costs. In order to understand how the bucket is getting used, leverage Storage lens. Storage lens has usage metrics which are free and activity metrics have a nominal fee of 20 cents per 1 million objects (refer to s3 pricing for details). Considering the data you get out of these metrics and the 15 month history, it is recommended to turn on. Activity metrics will tell you how your bucket is utilized. Here's a great blog to learn more about it:

https://aws.amazon.com/blogs/aws/s3-storage-lens/

If you want to dive deeper on the activity then turn on CloudTrail and S3 Server logs. You can find out what's the difference in activity reporting available from each. https://docs.aws.amazon.com/AmazonS3/latest/userguide/logging-with-S3.html

Overall leverage the tools to dive deeper into the S3 usage to understand the access pattern to optimize your cost.