Do check how aws charge for their services using this calculator https://calculator.aws/#/ For aurora, if you are not using aurora serverless, you are charged for $/hr minimally even without activity as explained in https://aws.amazon.com/rds/aurora/pricing/ As for how to check your bill, navigate to aws bills page explained in https://aws.amazon.com/aws-cost-management/aws-billing/ . To sum up, please get yourself trained up on how to operate in an AWS environment to prevent cases such as this.

With Serverless v2, the hourly cost is somewhere like 12-20 cents per ACU per hour, depending on the AWS Region. You can check the price for each combination of AWS Region and Aurora database engine here: https://aws.amazon.com/rds/aurora/pricing/ Let's consider us-east-1, which (as of January 2024) is 12 cents per ACU per hour. The minimum for Serverless v2 is 0.5 ACUs, so 6 cents / hour. A typical month has 720 hours (30 days) or 744 (31 days). So if you set minimum capacity to 0.5 ACUs, leave the cluster idle, and nothing unexpected happens, best case is roughly $43-45 per month for instance charges. Plus whatever usage-based charges for storage, I/O, and there are some other optional features that could result in charges. (That's why you would go through the exercise with the pricing calculator.) What could interfere with the best case? Turning on memory-consuming or CPU-consuming features could prevent the idle cluster from scaling down to 0.5 ACUs. Something like Performance Insights (minimum 2 ACUs) or global database (minimum 8 ACUs). Cleanup operations like PostgreSQL vacuum could run and cause scaling up when you think the database should be idle. What actions could you take to make the best case even better? Do "stop cluster" overnight or other long periods when you don't need to use the database. If you need to add reader instances to the cluster to test out multi-AZ usage (read/write splitting etc.), delete the reader instances when they're not needed. Have cron jobs to run stop-db-cluster, modify-db-cluster, etc. to put things into a cheaper state during overnight periods if you forget to do it at the end of the day.