What is an AWS RDS Instance

With Amazon RDS Reserved Instances, you have the option to reserve a DB Instance for one to three years in return for a significant discount compared to the On-Demand Instance price for that DB Instance.

There are three payment options to choose from when purchasing a Reserved Instance. With the Full Prepayment option, you prepay for the entire Reserved Instance. This option gives you the highest discount compared to On-Demand Instances. With the partial prepayment option, you make a low prepayment. You will then be billed at a reduced hourly rate for the entire term of the Reserved Instance. The "no prepayment" option does not require prepayment and offers a reduced hourly rate over the entire term.

All Reserved Instance types are available for the database engines Aurora, MySQL, MariaDB, PostgreSQL, Oracle and SQL Server.

  • Reserved Instances are offered with three payment options: prepayment, partial prepayment, and no prepayment.
  • With Reserved Instances you can save up to 69% compared to on-demand plans with constant use.
  • For Reserved Instances, you don't need to customize the way you use Amazon RDS. When compiling your invoice, our system automatically applies the Reserved Instance tariffs first to minimize your costs. For an instance hour, the On-Demand rate will only be charged if the total number of your instances running that hour exceeds the number of that booked instances.
  • Reserved Instances for the database engines MySQL, MariaDB, PostgreSQL and Amazon Aurora as well as for the “Bring your own license” (BYOL) edition of the Oracle database engine offer flexibility in terms of instance size.
  • All Reserved Instances that are prepaid or partially prepaid can be booked for terms of one or three years. Unpaid Reserved Instances are only available for one year.
  • Reserved Instances are available in all AWS Regions.
  • Reserved Instances are available for all supported DB engines.
  • For Reserved Instance pricing, see the Amazon RDS Pricing page.

For more information, see the Amazon RDS User Guide.

Reserved Instances are a great option for stable usage. Most production applications require database servers to be available 24/7. If you are still using On-Demand DB Instances for your production applications, Reserved Instances offer significant savings to your business.

Reserved Instances can also provide significant cost savings for business-critical applications that run on Multi-AZ database deployments for greater availability and data persistence.

You can determine whether Reserved Instances or On-Demand DB Instances better suit your needs by comparing the On-Demand hourly rates and the effective hourly rate of Reserved Instances. You can determine the effective hourly rate by spreading the one-time fee over the term and adding the one-hour portion to the hourly rate.

  • RIs with no prepayment - No upfront RIs offer a substantial discount (typically 30%) compared to on-demand prices. You do not make any prepayment, but you agree to pay for the Reserved Instance during the Reserved Instance term. This option is only offered with a one-year term.
  • RIs with partial prepayment - RIs with partial prepayment offer a higher discount than RIs without prepayment (usually around 60% for a term of 3 years). You pay for part of the Reserved Instance upfront and the remainder over a period of one or three years. This option strikes a good balance between prepayment and the hourly rate.
  • RIs with prepayment - Prepaid RIs offer the highest discount of any RI payment option (typically around 63% for a 3 year term). You pay upfront for Reserved Instances for the full term (one or three years) and receive the best effective hourly rate compared to running the same DB Instance on an on-demand basis.

To reduce costs, the usage of running DB Instances is first compared to your active Reserved Instances. For each hour, all running DB Instances are billed at the hourly rate for Reserved Instances as long as the number of running instances does not exceed the applicable Reserved Instances you own. Any usage of running DB Instances that exceeds the number of applicable Reserved Instances you have purchased will be charged the On-Demand rate.

For example, if you have 3 Reserved Instances with the same database engine and instance type (or the same instance family if size flexibility applies) in a particular region, the billing system will check every hour to see how many instances have been executed in total that match these parameters. If 3 or fewer instances are running, you will be charged the Reserved Instance rate for each instance running that hour. If more than 3 instances are running, you will be charged the On-Demand plan for the additional instances.

If you purchase a Reserved Instance in a particular region in which you already have an applicable running DB Instance, the benefit of the newly purchased Reserved Instance is automatically transferred to the DB Instance.

Amazon RDS Reserved Instances offer size flexibility for the database engines MySQL, MariaDB, PostgreSQL and Amazon Aurora as well as for the “Bring your own license” (BYOL) edition of the Oracle database engine. Due to the size flexibility, your preferential rate for Reserved Instances is automatically applied to use of any size within the instance family (using the same database engine). Size flexibility meets Not to Microsoft SQL Server and the License Included (LI) edition from Oracle.

For example, suppose you purchased a db.m4.2xlarge MySQL Reserved Instance in the US East (N.Virginia) region. The preferential rate for this RI automatically applies to MySQL instances of type 2 db.m4.xlarge without you having to do anything.

The RI special price also applies to the use of Single-AZ and Multi-AZ configurations of the same database engine and instance family. Let's assume you have bought a PostgreSQL Reserved Instance of the type db.r3.large for a single AZ in the EU (Frankfurt) region. The special price for this RI automatically applies in the same region to 50% of the use of a PostgreSQL Reserved Instance of the same type (db.r3.large) for a Multi-AZ.

Reserved Instances can be purchased through the AWS Management Console, the AWS command line interface, or the AWS API.

  1. Sign in to the AWS Management Console and select RDS under Databases.
  2. Select the region in which you want to buy the Reserved Instance.
  3. Select the Reserved Instances option in the navigation pane and click the Buy Reserved DB Instance button.
  4. Select the database engine, DB instance class, deployment type, and runtime. You can also enter an optional reference number for your purchase.
  5. Adjust the amount of Reserved DB Instances to be purchased.
  6. Click Next, review the information, and confirm the purchase.
  • Reserved Instance pricing only covers the cost of the instance. Storage and data transfer are billed separately.
  • Region, DB Engine, DB Instance class, deployment type and term must be selected when booking and cannot be changed later.
  • You can purchase up to 40 Reserved Instances. If you need additional Reserved Instances, fill out this form.
  • Reserved Instances cannot be transferred, resold, or canceled, and the one-time fee is non-refundable.