Purchase reserved capacity for your Amazon DynamoDB tables in order to receive a significant discount on the hourly charges. Reserved capacity is a billing feature that enables you to obtain discounts on your provisioned DynamoDB throughput capacity in exchange for a one-time up-front payment and commitment to a certain usage level. DynamoDB reserved capacity applies to a specific AWS region and can be purchased with 1-year or 3-year terms. The cost savings when using reserved capacity over on-demand provisioned capacity are up to 76% depending on the selected commitment term. A term of one year offers a 53% discount on provisioned throughput and a term of three years offers a 76% discount. Reserved capacity is applied to the aggregate capacity of all DynamoDB tables available within a specified AWS region. The capacity units provisioned beyond your reserved capacity will be billed at standard (i.e. on-demand) rates. To save even more money using DynamoDB reserved capacity pricing model, you have to predict the read and write capacity required for your DynamoDB tables within a given region: reserve too little capacity and you will end up paying on-demand prices where you could have had a discount; reserve too much and you will pay for capacity that gets unused, as you are being charged regardless whether or not you consume the provisioned capacity. To determine how much read and write capacity you can safely reserve you need to check your DynamoDB CloudWatch metrics. The CloudWatch metrics used to determine how much of your DynamoDB provisioned throughput is consumed are ConsumedReadCapacityUnits and ConsumedWriteCapacityUnits – the number of read/write capacity units consumed over a specified time period (Units: Count).
Costoptimisation
The reserved capacity pricing model represent a good strategy to cut down your Amazon DynamoDB costs. By reserving your DynamoDB read and write capacity units ahead of time, you can obtain significant cost savings compared to on-demand (standard) model.
Note 1: DynamoDB reserved capacity is applied to the total provisioned capacity within the AWS region in which you purchased your reserved capacity units. For example, if you purchased 10,000 read capacity units of reserved capacity, you can apply these to one table with 10,000 read capacity units, to 100 tables with 100 read capacity units or to 1000 tables with 10 read capacity units.
Note 2: You can reserve read or write capacity in quantities of up to 100,000 units. If you need to reserve more than 100,000 capacity units, you can make multiple capacity reservations. To get assistance for reserving DynamoDB capacity, you can open an AWS support case using the following parameters:
- Regarding: Account and Billing Support
- Service: Account
- Category: Other Account Issues
- Subject: "I need to reserve more than 100,000 Amazon DynamoDB capacity units
Audit
To determine if your Amazon DynamoDB tables are using the reserved capacity pricing model, perform the following actions:
Note: Verifying DynamoDB reserved read and write capacity using the AWS Command Line Interface (CLI) is not currently supported.Remediation / Resolution
Before you purchase reserved capacity for your Amazon DynamoDB tables, you need to determine how much read and write capacity throughput your tables consume using the **ConsumedReadCapacityUnits** and **ConsumedWriteCapacityUnits** metrics. The data recorded by these CloudWatch metrics will help you achieve a more reliable understanding of your DynamoDB usage patterns and predict the amount of units needed. To determine the right amount of read and write capacity units required by DynamoDB tables within a particular AWS cloud region and purchase the necessary reserved capacity, perform the following actions:
Note: Purchasing reserved read and write capacity units using the AWS Command Line Interface (CLI) is not currently supported.