Where data stored if I use Glacier Flexible Retrieval class?

Hi

S3 Glacier Flexible Retrieval is a Storage Class within Amazon S3. You can use normal S3 commands for delete object operations as shown below:

https://docs.aws.amazon.com/AmazonS3/latest/userguide/delete-objects.html

Above reference is when an object is stored in S3 Glacier Flexible Retrieval. Glacier vault has its own set of APIs.