What AWS Services support reserved nodes size flexibility or Reserved Instances size flexibility?

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The following AWS services support either reserved nodes size flexibility or Reserved Instances size flexibility:

• Amazon Elastic Compute Cloud (Amazon EC2). For more information, see How Reserved Instance discounts are applied.
• Amazon Relational Database Services (Amazon RDS). For more information, see Reserved DB instances for Amazon RDS.
• Amazon DynamoDB. For more information, see Amazon DynamoDB reservations.
• Amazon MemoryDB. For more information, see Overview of reserved nodes.
• Amazon ElastiCache. For more information, see ElastiCache reserved nodes.

For reserved nodes or Reserved Instances that are used and don't support size flexibility, you might incur additional charges.

Important: Amazon OpenSearch Service Reserved Instances and Amazon Redshift reserved nodes don't support size flexibility.

Example: Service that supports size flexibility

Suppose you have an EC2 Regional Reserved Instance m5.2xlarge in a specific AWS Region, and the instance supports instance size flexibility. In the same Region, your discounted rate might apply towards the usage of one m5.2xlarge instance or two m5.xlarge instances.

Example: Service that doesn't support size flexibility

Suppose you have purchased six c5.xlarge.search OpenSearch reserved instances in a specific Region. In the same Region, you have three c5.2xlarge.search nodes running with the same engine type as the reserved instance. If there aren't any other c5 family nodes running, then there's no match for your Reserved Instances.

If you purchase ten c5.xlarge.search reserved instances, and have four c5.2xlarge.search instances and two c5.xlarge.search instances running, then only two c5.xlarge.search instances match. For all other instances that don't match, size flexibility isn't supported.

Note: Amazon Redshift follows the same logic as seen in the preceding examples. For DynamoDB, you reserve read and write throughput capacity, not a reserve node or reserve instance.

Related information

Purchasing Amazon Redshift reserved nodes

Reserved Instances in Amazon OpenSearch Service

Supported instance types in Amazon OpenSearch Service