Tutorial: Configure your EC2 Fleet to launch instances into Interruptible Capacity Reservations

This tutorial walks you through the steps that you must perform so that your EC2 Fleet launches instances into Interruptible Capacity Reservations.

Interruptible Capacity Reservations represent spare capacity lent to you by On-Demand Capacity Reservation owners within your AWS organization. These reservations are suitable for interruptible workloads because the capacity owner can reclaim the capacity at any time with a 2-minute interruption notice, after which EC2 terminates the instances. For more information about Interruptible Capacity Reservations, see Interruptible Capacity Reservations.

The target capacity of the EC2 Fleet request should be less than or equal to the available capacity of the Interruptible Capacity Reservation that you are targeting. If the target capacity request exceeds the available capacity of your Interruptible Capacity Reservation, EC2 Fleet launches as many instances as it can and reports the launched instances in the API response.

Instances running in an Interruptible Capacity Reservation continue to run until you manually stop or terminate them, or until the capacity owner reclaims the capacity. When the capacity owner reclaims the capacity, Amazon EC2 sends an Amazon EventBridge notification 2 minutes before terminating the instances.

Considerations

Verify permissions

Before creating an EC2 Fleet, verify that you have an IAM role with the required permissions. For more information, see EC2 Fleet prerequisites.

To launch instances into an Interruptible Capacity Reservation, you must perform the following steps:

Step 1: Create a launch template

Use the create-launch-template command to create a launch template that specifies the Interruptible Capacity Reservation to target. In the launch template, set MarketType to interruptible-capacity-reservation and specify the CapacityReservationId of your Interruptible Capacity Reservation.

Example launch template configuration:

{
    "LaunchTemplateName": "interruptible-cr-launch-template",
    "LaunchTemplateData": {
        "InstanceType": "m5.large",
        "ImageId": "ami-0abcdef1234567890",
        "CapacityReservationSpecification": {
            "CapacityReservationTarget": {
                "CapacityReservationId": "cr-0123456789abcdef0"
            }
        },
        "InstanceMarketOptions": {
            "MarketType": "interruptible-capacity-reservation"
        }
    }
}

Example output

{
    "LaunchTemplate": {
        "LaunchTemplateId": "lt-0123456789example",
        "LaunchTemplateName": "interruptible-cr-launch-template",
        "CreateTime": "2026-03-12T10:00:00.000Z",
        "CreatedBy": "arn:aws:iam::123456789012:user/Admin",
        "DefaultVersionNumber": 1,
        "LatestVersionNumber": 1
    }
}

For more information, see Create an Amazon EC2 launch template.

Step 2: Configure the EC2 Fleet

Create a configuration file for the EC2 Fleet that specifies the launch template and target capacity. The following configuration uses the launch template interruptible-cr-launch-template that you created in Step 1.

You must specify ReservedCapacityOptions with ReservationType set to interruptible-capacity-reservation when using reserved-capacity as the DefaultTargetCapacityType.

Create a file named config.json with the following content:

{
    "LaunchTemplateConfigs": [
        {
            "LaunchTemplateSpecification": {
                "LaunchTemplateName": "interruptible-cr-launch-template",
                "Version": "1"
            },
            "Overrides": [
                {
                    "InstanceType": "m5.large",
                    "AvailabilityZone": "us-east-1a"
                }
            ]
        }
    ],
    "TargetCapacitySpecification": {
        "TotalTargetCapacity": 10,
        "DefaultTargetCapacityType": "reserved-capacity"
    },
    "ReservedCapacityOptions": {
        "ReservationType": ["interruptible-capacity-reservation"]
    },
    "Type": "instant"
}

Key configuration parameters:

Step 3: Launch the fleet and view results

Use the create-fleet command to create the fleet:

aws ec2 create-fleet \
    --cli-input-json file://config.json

After you create the instant fleet using the preceding configuration, EC2 Fleet launches 10 instances into the Interruptible Capacity Reservation to meet the target capacity.

Example output

{
    "FleetId": "fleet-12345678-1234-1234-1234-123456789012",
    "Instances": [
        {
            "LaunchTemplateAndOverrides": {
                "LaunchTemplateSpecification": {
                    "LaunchTemplateId": "lt-0123456789example",
                    "Version": "1"
                },
                "Overrides": {
                    "InstanceType": "m5.large",
                    "AvailabilityZone": "us-east-1a"
                }
            },
            "Lifecycle": "interruptible-capacity-reservation",
            "InstanceIds": [
                "i-0123456789example1",
                "i-0123456789example2",
                "i-0123456789example3",
                "i-0123456789example4",
                "i-0123456789example5",
                "i-0123456789example6",
                "i-0123456789example7",
                "i-0123456789example8",
                "i-0123456789example9",
                "i-0123456789example0"
            ],
            "InstanceType": "m5.large",
            "Platform": "Linux/UNIX"
        }
    ],
    "Errors": []
}

For more information, see Create an EC2 Fleet.

Clean up

To stop incurring charges, terminate the instances when they are no longer needed. Note that EC2 also terminates instances launched into an Interruptible Capacity Reservation automatically when the capacity owner reclaims the capacity.

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