DynamoDB Pricing Provisioned vs On-Demand

1

I feel like I am calculating cost incorrectly for DynamoDB

When looking at the Provisioned Pricing, a WCU, (one write request under 1KB) is $.00065
Then, 1,000,000 write requests in a month to a table under the provisioned pricing model would be $650.

Whereas with the On-Demand Pricing 1,000,000 writes is a flat $1.50 per every million.

That would be a drastic savings in using the On-Demand Pricing instead of the Provisioned, but the documentation seems to say that the Provisioned is cheaper if you properly plan the usage of your back-end.

asked 5 years ago5694 views
3 Answers
1

Hi,
First, I would not use pricing as the starting point to choose between provisioned versus on-demand capacity mode. The workload and business requirements will drive the decision. When your traffic patterns are unknown, when you are creating new tables, or if you have an unpredictable traffic pattern, on-demand will work best for your use case.
https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/HowItWorks.ReadWriteCapacityMode.html

Second, let's take a closer look at the pricing. Provisioned capacity bills you every hour for the provisioned capacity. Whereas on-demand bills you per request. The differences are clear when you break it down to the per second write request rates. Let's assume your application expects 10M writes per month and writes are spread evenly over time. You are driving approximately 10M/31/24/60/60 = ~4 writes per second. You will provision 4 WCUs on your table. 4 WCUs translate to roughly $0.00065 ** 4 WCU ** 24 hours * 31 days = $1.9344 per month. Checkout the FreeTier - You get 25 WCUs and 25 RCUs of provisioned capacity for free each month. Your calculations for on-demand are correct. Checkout the pricing examples at the bottom of this page for additional info: https://aws.amazon.com/dynamodb/pricing/provisioned/

AWS
answered 5 years ago
0

Thank you so much, I understand now :)

answered 5 years ago
0

Happy to help. Have a good day.

AWS
answered 5 years ago

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