Savings Plan for Lambda

Savings plans will give a discount to AWS Lambda duration pricing, as accrued per hour (unused saving plans don't roll over to the next hour). Savings can be found here: https://aws.amazon.com/savingsplans/pricing/ and range from 12% to 17% depending on payment options and commitment.

Once you have a savings plan in place, the Lambda function duration costs will be charged at the discounted rate, up until the savings plan limit. Note that Savings Plans apply across compute costs in the account, and will be applied to the services that offer the biggest discounts first, which means that if you have EC2 instances, they may consume the discount (since it will save you more money).

Buying a Savings Plan purely for Lambda is really hard, since the discounts apply to spend in each hour (not the overall average), and Lambda functions tend to be bursty and unpredictable in nature. So (in a contrived example), if you buy a $1 per/hour Savings Plan, and have a Lambda function that is idle for almost all of the month which then bursts to $730 of usage in a single hour, you will get a discount of 12-17% for ~$1 of the $730 spend in that hour, and no other discount that month (since there was no Lambda spend).

In essence, if you're trying to buy a Savings Plan just for Lambda usage, you should probably only look to purchase one that covers the minimum spend that's incurred each and every hour - otherwise you will have wasted Savings Plans commitment for every hour that the Lambda function usage is below the spend.

Example here: https://docs.aws.amazon.com/savingsplans/latest/userguide/sp-applying.html#scenario-1