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# AWS::EC2::EC2Fleet CapacityReservationOptionsRequest

Describes the strategy for using unused Capacity Reservations for fulfilling On-Demand capacity.
**Note** 
This strategy can only be used if the EC2 Fleet is of type `instant`.
For more information about Capacity Reservations, see [On-Demand Capacity Reservations](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-capacity-reservations.html) in the *Amazon EC2 User Guide*. For examples of using Capacity Reservations in an EC2 Fleet, see [EC2 Fleet example configurations](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-fleet-examples.html) in the *Amazon EC2 User Guide*.
## Syntax

To declare this entity in your CloudFormation template, use the following syntax:
### JSON

```
{
 "[UsageStrategy](#cfn-ec2-ec2fleet-capacityreservationoptionsrequest-usagestrategy)" : {{String}}
}
```
### YAML

```
 [UsageStrategy](#cfn-ec2-ec2fleet-capacityreservationoptionsrequest-usagestrategy): {{String}}
```
## Properties

`UsageStrategy` 
Indicates whether to use unused Capacity Reservations for fulfilling On-Demand capacity. 
If you specify `use-capacity-reservations-first`, the fleet uses unused Capacity Reservations to fulfill On-Demand capacity up to the target On-Demand capacity. If multiple instance pools have unused Capacity Reservations, the On-Demand allocation strategy (`lowest-price` or `prioritized`) is applied. If the number of unused Capacity Reservations is less than the On-Demand target capacity, the remaining On-Demand target capacity is launched according to the On-Demand allocation strategy (`lowest-price` or `prioritized`). 
If you do not specify a value, the fleet fulfils the On-Demand capacity according to the chosen On-Demand allocation strategy. 
*Required*: No 
*Type*: String 
*Allowed values*: `use-capacity-reservations-first` 
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