On-Demand Capacity Reservations - Amazon Elastic Compute Cloud
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On-Demand Capacity Reservations

On-Demand Capacity Reservations enable you to reserve compute capacity for your Amazon EC2 instances in a specific Availability Zone for any duration. Capacity Reservations mitigate against the risk of being unable to get On-Demand capacity in case there are capacity constraints. If you have strict capacity requirements, and are running business-critical workloads that require a certain level of long or short-term capacity assurance, we recommend that you create a Capacity Reservation to ensure that you always have access to Amazon EC2 capacity when you need it, for as long as you need it.

The following are some common use cases for Capacity Reservations:

  • Disaster recovery — you can reserve capacity in a different Availability Zone or Region to ensure that the capacity you need is available during a fail over event.

  • Regulatory requirements — you can use Capacity Reservations to satisfy regulatory requirements for high availability. Capacity Reservations ensure that capacity is in place to meet those requirements, even if you aren't utilizing those resources.

  • Events — you can create Capacity Reservations before your business-critical events to ensure that you can scale when you need to.

You can create Capacity Reservations at any time, without entering into a one-year or three-year term commitment. The capacity becomes available and billing starts as soon as the Capacity Reservation is provisioned in your account. When you no longer need the capacity assurance, cancel the Capacity Reservation to release the capacity and to stop incurring charges. You can also use the billing discounts offered by Regional Reserved Instances to reduce the cost of a Capacity Reservation.

When you create a Capacity Reservation, you specify:

  • The Availability Zone in which to reserve the capacity

  • The number of instances for which to reserve capacity

  • The instance attributes, including the instance type, tenancy, and platform/OS

Capacity Reservations can only be used by instances that match their attributes. By default, they are automatically used by running instances that match the attributes. If you don't have any running instances that match the attributes of the Capacity Reservation, it remains unused until you launch an instance with matching attributes.

Supported platforms

You must create the Capacity Reservation with the correct platform to ensure that it properly matches with your instances. Capacity Reservations support the following platforms:

  • Windows

  • Windows with SQL Server

  • Windows with SQL Server Web

  • Windows with SQL Server Standard

  • Windows with SQL Server Enterprise

When you purchase a Capacity Reservation, you must specify the platform that represents the operating system for your instance.

  • For Windows with SQL Standard, Windows with SQL Server Enterprise, and Windows with SQL Server Web, you must choose the specific platform.

  • For all other Windows versions, excluding BYOL which is not supported, choose the Windows platform.

For more information about the supported Linux platforms, see Supported platforms in the Amazon EC2 User Guide for Linux Instances.


The number of instances for which you are allowed to reserve capacity is based on your account's On-Demand Instance quota. You can reserve capacity for as many instances as that quota allows, minus the number of instances that are already running.

Quotas apply to running instances only. If your instance is pending, stopping, stopped, or hibernated, it does not count towards your quota.


Before you create Capacity Reservations, take note of the following limitations and restrictions.

  • Active and unused Capacity Reservations count toward your On-Demand Instance limits.

  • Capacity Reservations are not transferable from one Amazon account to another. However, you can share Capacity Reservations with other Amazon accounts. For more information, see Work with shared Capacity Reservations.

  • Zonal Reserved Instance billing discounts do not apply to Capacity Reservations.

  • Capacity Reservations can be created in cluster placement groups. Spread and partition placement groups are not supported.

  • Capacity Reservations can't be used with Dedicated Hosts. Capacity Reservations can be used with Dedicated Instances.

  • Capacity Reservations can't be used with Bring Your Own License (BYOL).

  • Capacity Reservations do not ensure that a hibernated instance can resume after you try to start it.