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    Elastic Compute Service:Immediate capacity reservations

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    Elastic Compute Service:Immediate capacity reservations

    Last Updated:Apr 21, 2026

    Reserve capacity for pay-as-you-go instances on demand, with reservations taking effect immediately upon purchase.

    Overview

    When you purchase an immediate capacity reservation, the specified resources are reserved for your exclusive use. Billing starts at the pay-as-you-go instance rate as soon as the reservation takes effect and continues regardless of whether you create instances. Billing stops when the reservation is released.

    When you purchase an immediate capacity reservation, you must specify attributes such as zone, instance type, and operating system. The system reserves matching resources in a private pool. You can then use the private pool to create pay-as-you-go instances with guaranteed capacity.

    Note

    Immediate Capacity Reservation guarantees resources only for pay-as-you-go instances, not spot instances.

    An immediate capacity reservation goes through the following phases in its lifecycle:

    1. Billing starts at the pay-as-you-go instance rate as soon as the reservation is purchased.

    2. During the validity period, you can use the reserved capacity in the private pool to create pay-as-you-go instances at any time.

    3. You can manually release the reservation or let it expire and be released automatically.

      Note

      When the reservation is released, existing pay-as-you-go instances remain unaffected and continue to run. These instances are billed at pay-as-you-go rates.

    The following figure shows how an immediate capacity reservation reserves resources for two instances.

    Billing

    Billing starts at the pay-as-you-go instance rate as soon as the reservation is purchased, regardless of whether you create instances. Billing stops when the reservation is released, either manually or upon expiration.

    Note

    Before you create instances from the private pool, you are charged only for the instance type. After you create pay-as-you-go instances, you are charged based on the full instance configuration, including the instance type, disks, and public bandwidth.

    Savings plans and regional reserved instances can offset the hourly bills of pay-as-you-go instances associated with immediate capacity reservations. Zonal reserved instances cannot.

    Limitations

    • Immediate Capacity Reservation is available only for specific instance types in specific regions. See the buy page for supported options.

    • A private pool can only create pay-as-you-go instances that match the instance type, zone, and operating system of the associated capacity reservation.

    • Zonal reserved instances cannot be applied to pay-as-you-go instances created from private pools.

    Use cases

    • High demand for elastic resources: Billing starts at the pay-as-you-go rate when a reservation is purchased. To maximize cost-effectiveness, fully utilize the reserved resources throughout the validity period.

    • Resource reservation with savings plans or regional reserved instances: Savings plans and regional reserved instances reduce costs but do not reserve capacity. Purchase immediate capacity reservations to guarantee resource availability alongside these plans.

    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 instance in the China (Hangzhou) region, applicable 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 as needed.

      Solution:

      • Create a manually releasable immediate capacity reservation in both Hangzhou Zone H and Hangzhou Zone I. Ensure the reservations match the instance type, quantity, and operating system of the regional reserved instance.

      • To reserve resources in other zones, release the reservations in Hangzhou Zone H and Zone I, then create new reservations in the target zones.

    • Scheduled release

      Requirements:

      • Apply a general-purpose savings plan to offset the hourly bills of pay-as-you-go instances.

      • Reserve different instance types for specific periods: ecs.c6e.large for the first half of the month and ecs.c6.large for the second half.

      Solution:

      • At the beginning of the month, purchase immediate capacity reservations for ecs.c6e.large and schedule them for release at a specified time.

      • In the middle of the month, purchase immediate capacity reservations for ecs.c6.large and schedule them for release at a specified time.