You can purchase immediate capacity reservations to reserve and lock down capacity for pay-as-you-go instances. Immediate capacity reservations take effect immediately after they are created, and are suitable for scenarios in which the resource demands are high.
Introduction
You can reserve capacity at any time by purchasing an immediate capacity reservation. After you purchase an immediate capacity reservation, the specified resources are reserved and locked down for your exclusive use. As soon as a capacity reservation takes effect, the reservation begins to be billed based on the pay-as-you-go instance rate. Billing continues regardless of whether the capacity reservation is used to create instances. Billing stops when the capacity reservation is released.
When you purchase an immediate capacity reservation, you must specify attributes such as zone, instance type, and operating system. The system uses a private pool to reserve resources that match the specified attributes. You can have guaranteed access to the reserved capacity in the private pool to create pay-as-you-go instances.
Immediate Capacity Reservation provides guaranteed resources only to create pay-as-you go instances but not preemptible instances.
An immediate capacity reservation goes through the following phases throughout its lifecycle:
As soon as the capacity reservation is purchased, it begins to be billed based on the pay-as-you-go instance rate.
You can use the reserved capacity in the associated private pool at any time during the validity period of the reservation to create pay-as-you-go instances.
You can manually release the capacity reservation or wait for it to expire and be automatically released.
NoteWhen the associated immediate capacity reservation is released, created pay-as-you-go instances remain unaffected and continue to run as expected. The instances are billed based on the pay-as-you-go rates after they are created.
The following figure shows how to use an immediate capacity reservation to reserve resources for two instances.
Billing
An immediate capacity reservation begins to be billed based on the pay-as-you-go instance rate as soon as the capacity reservation is purchased. Billing continues regardless of whether the capacity reservation is used to create instances. Billing stops when the capacity reservation is automatically released upon expiration or manually released.
Before a private pool associated with a capacity reservation is used to create pay-as-you-go instances, you are charged only for the specified instance type. After the capacity reserved by the capacity reservation is used to create pay-as-you-go instances, you are charged based on the instance configurations including the instance type, disks, and public bandwidth.
Savings plans and regional reserved instances can be applied to offset the hourly bills of the pay-as-you-go instances associated with immediate capacity reservations, but zonal reserved instances cannot.
Limits
Immediate Capacity Reservation is available only for specific instance types in specific regions. For more information, see the buy page.
The reserved capacity in a private pool can be used to create only pay-as-you-go instances that match the instance type, zone, and operating system attributes of the associated capacity reservation.
Zonal reserved instances cannot be applied to the pay-as-you-go instances that are created from reserved resources in private pools.
Scenarios
High requirements for elastic resources: When an immediate capacity reservation is purchased, billing starts based on the pay-as-you-go rate of the instance type. To use resources in the most cost-effective manner, you must make continuous and full use of the reserved resources during the validity period of the capacity reservation.
Requirements for reserved resources in use of savings plans or regional reserved instances: Savings plans and regional reserved instances can significantly reduce costs but cannot provide resource reservations. To reserve resources when you have savings plans or regional reserved instances, you can purchase immediate capacity reservations.
Usage examples
Manual release
Requirements:
Apply one regional reserved instance to offset the hourly bills of pay-as-you-go instances. The reserved instance is an ecs.g6.large Linux reserved instance in the China (Hangzhou) region and can be applied to 10 ecs.g6.large instances.
Immediately reserve resources in Hangzhou Zone H and Hangzhou Zone I.
Switch to other zones to create pay-as-you-go instances based on your business requirements.
Solution:
Create an immediate capacity reservation that can be manually released in both Hangzhou Zone H and Hangzhou Zone I. Make sure that the created immediate capacity reservations match the instance type, instance quantity, and operating system attributes of the regional reserved instance.
To reserve resources in other zones, manually release the immediate capacity reservations in Hangzhou Zone H and Hangzhou Zone I and create immediate capacity reservations within the zones where you want to reserve resources.
Scheduled release
Requirements:
Apply a general-purpose savings plan that you purchased to offset the hourly bills of pay-as-you-go instances.
Reserve resources of different instance types for specific periods of time. Reserve resources of the ecs.c6e.large instance type for the first half of a month and resources of the ecs.c6.large instance type for the second half of the month.
Solution:
At the beginning of the month, purchase immediate capacity reservations for the ecs.c6e.large instance type and schedule the reservations to be released at the specified time.
In the middle of the month, purchase immediate capacity reservations for the ecs.c6.large instance type and schedule the reservations to be released at the specified time.