I'm exploring the possibility to backup an Aurora Serverless cluster with AWS Backup, in order to cover a much more extended period than the 35 days of automated backups RDS offers. The aim is to get to 6 months to 1 year of daily cluster backups, depending on how much will it cost. So far, I have an idea on how to set it up using CDK; what I miss is the costs.
I still have no clue about how the billing for cluster backup is calculated. For what I've seen, backup storage is 0,0021 $/GB per month in my region, and from the last billing I've taken from AWS, the cost for cluster backups totals to around 14$. Which means that I have around 660 GB for "additional backup storage", but that doesn't seem right. Our daily snapshots are around 80-90 GB of size, so by a quick calculation, that would add to around 3100 GB of cluster size, which is far more than 660 GB. So where this discrepancy in price comes from?