AWS Pricing Calculator got GB-seconds calculation for Lambda snapstart cache wrong
Hello all,
Below is a screenshot of the issue. The AWS pricing calculator miscalculates the GB-seconds of snapstart cache. The sample shown has 30 days, which is 30243600 seconds (2,592,000), and for 10 GB of memory this should be 25,920,000 GB-seconds, but instead it shows 7200, meaning that the seconds were calculated as 720.
This issue also occurs if you change the units of the first field to hours instead of days.
Regards, Yassin
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Thank you for bringing this to our attention. You're absolutely correct in your calculation. For a Lambda function with 10 GB of allocated memory running for 30 days, the SnapStart cache GB-seconds should indeed be calculated as:
30 days × 24 hours × 3600 seconds = 2,592,000 seconds 2,592,000 seconds × 10 GB = 25,920,000 GB-seconds
The value of 7200 shown in the calculator appears to be significantly underestimating the actual GB-seconds, which would affect the accuracy of your cost estimates for SnapStart cache charges.
For SnapStart, you're charged for caching and maintaining the snapshot for as long as your function version remains active, with a minimum charge of 3 hours. The pricing is based on the amount of memory allocated to your function multiplied by the time the function version is active.
I recommend reporting this calculation error directly through the AWS Support Center at https://console.aws.amazon.com/support/ so the AWS Pricing Calculator team can investigate and correct this issue. In the meantime, you may want to manually calculate your SnapStart cache costs using the correct formula to ensure accurate cost planning for your Lambda functions.
To verify your costs, you can use the SnapStart cache pricing rate for your region (typically around $0.0000015046 per GB-second in US regions) and multiply it by your correctly calculated GB-seconds value.
Sources
AWS Lambda Pricing
Improving startup performance with Lambda SnapStart - AWS Lambda
