RDS billing went extremely high

Hi there, and Happy New Year to you. It's difficult to say exactly what's driving this cost without more information about your workload, but I can help interpret what you're seeing here and offer some suggestions on how you might find some additional information.

The usage quantity you've highlighted above is the sum of all your usage of that type (i.e. db.m6gd.large instances running multi-AZ MySQL in us-east-2). If you had a single instance running around the clock for the entire month I would also expect that number to be 744 hours. The fact that it's higher says to me that you had more than one such RDS instance running at a time for some or all of December.

I would suggest looking in Cost Explorer with daily granularity for the month of December (see below). Narrowing down when the charges occurred may be enough to help explain them.

Another option would be to use AWS Data Exports. These can give you a very detailed accounting for your AWS usage down to individual resources, though it is more complex than Cost Explorer would be.

Finally billing support is available to all AWS customers regardless of their support level. If you're unable to explain this usage on your own with the above tools then I would suggest reaching out to them via Support Center.

Do or have you had more than 1 RDS Instance in us-east-2? This bill should have a total number of hours for the specific instance type.

You are able in the AWS Support console raise Billing Issues. If the bill doesnt look correct, I would raise a billing enquiry.