Bill on NAT gateways

The charges are rounded up to an hour if the usage is less than an hour. That's why you were charged for two hours. Here is the AWS Documentation for further details: https://aws.amazon.com/vpc/pricing/

If price is a major concern, you can host your own NAT instances and configure it but you would have to take care of the scalability and availability yourself. More details here: https://docs.aws.amazon.com/vpc/latest/userguide/VPC_NAT_Instance.html

You haven't mentioned your use case but you can look into VPC endpoints to see if they fit your usecase. More details here: https://docs.aws.amazon.com/whitepapers/latest/aws-privatelink/what-are-vpc-endpoints.html

It's normal to be billed for a full hour even if you only used the NAT gateways for 10 minutes. AWS charges for NAT gateways on an hourly basis, regardless of actual usage time within that hour. This means that even if you use a NAT gateway for just a few minutes, you'll be billed for the full hour.

To avoid incurring such charges in the future, consider the following strategies:

1. Plan your usage carefully: If you know you'll only need NAT gateways for a short time, try to consolidate your work within a single hour to minimize costs.

2. Delete NAT gateways when not in use: If you don't need the NAT gateways continuously, make sure to delete them after your work is done. You can always create new ones when needed.

3. Use alternatives when possible: For some workloads, you might be able to use other solutions like VPC endpoints for AWS services or placing resources in public subnets if appropriate for your use case.

4. Monitor your usage: Regularly check your AWS Cost Explorer to keep track of your NAT gateway usage and costs.

5. Consider using AWS Budgets: Set up alerts to notify you when your NAT gateway costs reach a certain threshold.

If you need further assistance or want to discuss your specific situation, you can reach out to AWS Support by creating a support case in the Support Center.

Remember, as a new user, it's important to regularly review your AWS resources and delete or stop any that you're not actively using to avoid unexpected charges.

Sources
Billings: how to calculate real NATGateway costs!? | AWS re:Post
Pricing for NAT gateways - Amazon Virtual Private Cloud
Billing regarding my vpc | AWS re:Post