Reserved DB instances for Aurora

Using reserved DB instances, you can reserve a DB instance for a one- or three-year term. Reserved DB instances provide you with a significant discount compared to on-demand DB instance pricing. Reserved DB instances are not physical instances, but rather a billing discount applied to the use of certain on-demand DB instances in your account. Discounts for reserved DB instances are tied to instance type and Amazon Web Services Region.

The general process for working with reserved DB instances is: First get information about available reserved DB instance offerings, then purchase a reserved DB instance offering, and finally get information about your existing reserved DB instances.

Overview of reserved DB instances

When you purchase a reserved DB instance in Amazon RDS, you purchase a commitment to getting a discounted rate, on a specific DB instance type, for the duration of the reserved DB instance. To use an Amazon RDS reserved DB instance, you create a new DB instance just like you do for an on-demand instance.

The new DB instance that you create must have the same specifications as the reserved DB instance for the following:

If the specifications of the new DB instance match an existing reserved DB instance for your account, you are billed at the discounted rate offered for the reserved DB instance. Otherwise, the DB instance is billed at an on-demand rate.

You can modify a DB instance that you're using as a reserved DB instance. If the modification is within the specifications of the reserved DB instance, part or all of the discount still applies to the modified DB instance. If the modification is outside the specifications, such as changing the instance class, the discount no longer applies. For more information, see Size-flexible reserved DB instances.

For more information about reserved DB instances, including pricing, see Amazon RDS reserved instances.

Offering types

Reserved DB instances are available in three varieties—No Upfront, Partial Upfront, and All Upfront—that let you optimize your Amazon RDS costs based on your expected usage.

If you are using consolidated billing, all the accounts in the organization are treated as one account. This means that all accounts in the organization can receive the hourly cost benefit of reserved DB instances that are purchased by any other account. For more information about consolidated billing, see Amazon RDS reserved DB instances in the Amazon Billing and Cost Management User Guide.

Aurora DB cluster configuration flexibility

You can use Aurora reserved DB instances with both DB cluster configurations:

Aurora automatically accounts for the price difference between these configurations. Aurora I/O-Optimized consumes 30% more normalized units per hour than Aurora Standard.

For more information about Aurora cluster storage configurations, see Storage configurations for Amazon Aurora DB clusters. For more information about pricing for Aurora cluster storage configurations, see Amazon Aurora pricing.

Size-flexible reserved DB instances

When you purchase a reserved DB instance, one thing that you specify is the instance class, for example db.r5.large. For more information about DB instance classes, see Aurora DB instance classes.

If you have a DB instance, and you need to scale it to larger capacity, your reserved DB instance is automatically applied to your scaled DB instance. That is, your reserved DB instances are automatically applied across all DB instance class sizes. Size-flexible reserved DB instances are available for DB instances with the same Amazon Web Services Region and database engine. Size-flexible reserved DB instances can only scale in their instance class type. For example, a reserved DB instance for a db.r5.large can apply to a db.r5.xlarge, but not to a db.r6g.large, because db.r5 and db.r6g are different instance class types.

Reserved DB instance benefits also apply for both Multi-AZ and Single-AZ configurations. Flexibility means that you can move freely between configurations within the same DB instance class type. For example, you can move from a Single-AZ deployment running on one large DB instance (four normalized units per hour) to a Multi-AZ deployment running on two medium DB instances (2+2 = 4 normalized units per hour).

Size-flexible reserved DB instances are available for the following Aurora database engines:

You can compare usage for different reserved DB instance sizes by using normalized units per hour. For example, one unit of usage on two db.r3.large DB instances is equivalent to eight normalized units per hour of usage on one db.r3.small. The following table shows the number of normalized units per hour for each DB instance size.

For example, suppose that you purchase a db.t2.medium reserved DB instance, and you have two running db.t2.small DB instances in your account in the same Amazon Web Services Region. In this case, the billing benefit is applied in full to both instances.

Alternatively, if you have one db.t2.large instance running in your account in the same Amazon Web Services Region, the billing benefit is applied to 50 percent of the usage of the DB instance.

Aurora reserved DB instance billing examples

The following examples illustrate the pricing for reserved DB instances for Aurora DB clusters using both the Aurora Standard and Aurora I/O-Optimized DB cluster configurations.

Example using Aurora Standard

The price for a reserved DB instance doesn't provide a discount for the costs associated with storage, backups, and I/O. The following example illustrates the total cost per month for a reserved DB instance:

Add all of these options ($138.70 + $45.60 + $20 + $30) with the reserved DB instance, and the total cost per month is $234.30.

If you choose to use an on-demand DB instance instead of a reserved DB instance, an Aurora MySQL Single-AZ db.r5.large DB instance class in US East (N. Virginia) costs $0.29 per hour, or $217.50 per month. So, for an on-demand DB instance, add all of these options ($217.50 + $45.60 + $20 + $30), and the total cost per month is $313.10. You save nearly $79 per month by using the reserved DB instance.

Example using an Aurora Standard DB cluster with two reader instances

To use reserved instances for Aurora DB clusters, simply purchase one reserved instance for each DB instance in the cluster.

Extending the first example, you have an Aurora MySQL DB cluster with one writer DB instance and two Aurora Replicas, for a total of three DB instances in the cluster. The two Aurora Replicas incur no extra storage or backups charges. If you purchase three db.r5.large Aurora MySQL reserved DB instances, your cost will be $234.30 (for the writer DB instance) + 2 * ($138.70 + $20 I/O per Aurora Replica), for a total of $551.70 per month.

The corresponding on-demand cost for an Aurora MySQL DB cluster with one writer DB instance and two Aurora Replicas is $313.10 + 2 * ($217.50 + $20 I/O per instance) for a total of $788.10 per month. You save $236.40 per month by using the reserved DB instances.

Example using Aurora I/O-Optimized

You can reuse your existing Aurora Standard reserved DB instances with Aurora I/O-Optimized. To fully use the benefits of your reserved instance discounts with Aurora I/O-Optimized, you can buy 30% additional reserved instances similar to your current reserved instances.

The following table shows examples of how to estimate the additional reserved instances when using Aurora I/O-Optimized. If the required reserved instances are a fraction, you can take advantage of the size flexibility available with reserved instances to get to a whole number. In these examples, "current" refers to the Aurora Standard reserved instances that you have now. Additional reserved instances are the number of Aurora Standard reserved instances that you must buy to maintain your current reserved instance discounts when using Aurora I/O-Optimized.

Example using an Aurora I/O-Optimized DB cluster with two reader instances

You have an Aurora MySQL DB cluster with one writer DB instance and two Aurora Replicas, for a total of three DB instances in the cluster. They use the Aurora I/O-Optimized DB cluster configuration. To use reserved DB instances for this cluster, you would need to buy four reserved DB instances of the same DB instance class. Three DB instances using Aurora I/O-Optimized consume 3.9 normalized units per hour, compared to 3 normalized units per hour for three DB instances using Aurora Standard. However, you save the monthly I/O costs for each DB instance.

Deleting a reserved DB instance

The terms for a reserved DB instance involve a one-year or three-year commitment. You can't cancel a reserved DB instance. However, you can delete a DB instance that is covered by a reserved DB instance discount. The process for deleting a DB instance that is covered by a reserved DB instance discount is the same as for any other DB instance.

You're billed for the upfront costs regardless of whether you use the resources.

If you delete a DB instance that is covered by a reserved DB instance discount, you can launch another DB instance with compatible specifications. In this case, you continue to get the discounted rate during the reservation term (one or three years).

Working with reserved DB instances

You can use the Amazon Web Services Management Console, the Amazon CLI, and the RDS API to work with reserved DB instances.

aws rds describe-reserved-db-instances-offerings

OFFERING  OfferingId                            Class         Multi-AZ  Duration  Fixed Price  Usage Price  Description  Offering Type
OFFERING  438012d3-4052-4cc7-b2e3-8d3372e0e706  db.r3.large   y         1y        1820.00 USD  0.368 USD    mysql        Partial  Upfront
OFFERING  649fd0c8-cf6d-47a0-bfa6-060f8e75e95f  db.r3.small   n         1y         227.50 USD  0.046 USD    mysql        Partial  Upfront
OFFERING  123456cd-ab1c-47a0-bfa6-12345667232f  db.r3.small   n         1y         162.00 USD   0.00 USD    mysql        All      Upfront
    Recurring Charges:   Amount  Currency  Frequency        
    Recurring Charges:   0.123   USD       Hourly
OFFERING  123456cd-ab1c-37a0-bfa6-12345667232d  db.r3.large   y         1y         700.00 USD   0.00 USD    mysql        All      Upfront
    Recurring Charges:   Amount  Currency  Frequency
    Recurring Charges:   1.25    USD       Hourly
OFFERING  123456cd-ab1c-17d0-bfa6-12345667234e  db.r3.xlarge  n         1y        4242.00 USD   2.42 USD    mysql        No       Upfront

aws rds purchase-reserved-db-instances-offering \
    --reserved-db-instances-offering-id 649fd0c8-cf6d-47a0-bfa6-060f8e75e95f \
    --reserved-db-instance-id MyReservation

aws rds purchase-reserved-db-instances-offering ^
    --reserved-db-instances-offering-id 649fd0c8-cf6d-47a0-bfa6-060f8e75e95f ^
    --reserved-db-instance-id MyReservation

RESERVATION  ReservationId      Class        Multi-AZ  Start Time                Duration  Fixed Price  Usage Price  Count  State            Description  Offering Type
RESERVATION  MyReservation      db.r3.small  y         2011-12-19T00:30:23.247Z  1y        455.00 USD   0.092 USD    1      payment-pending  mysql        Partial  Upfront

aws rds describe-reserved-db-instances

RESERVATION  ReservationId     Class        Multi-AZ  Start Time                Duration  Fixed Price  Usage Price  Count  State    Description  Offering Type
RESERVATION  MyReservation     db.r3.small  y         2011-12-09T23:37:44.720Z  1y        455.00 USD   0.092 USD    1      retired  mysql        Partial  Upfront

Viewing the billing for your reserved DB instances

You can view the billing for your reserved DB instances in the Billing Dashboard in the Amazon Web Services Management Console.