spot fleet for on demand instance

While you can create a Spot Fleet request that includes only On-Demand Instances, this approach doesn't align with the primary purpose of Spot Fleet, which is designed to help you leverage Spot Instances alongside On-Demand Instances.

Spot Fleet allows you to specify a mix of On-Demand and Spot Instances. You can configure your Spot Fleet request to include a specific amount of On-Demand capacity by setting the "OnDemandTargetCapacity" parameter. For example, you could set your total target capacity to 10 and your On-Demand target capacity to 10, which would effectively create a fleet of only On-Demand Instances.

However, if you're specifically looking to launch only On-Demand Instances, there are more appropriate AWS services to use:

1. For simple one-time launches, the EC2 RunInstances API is more straightforward.

2. For managed instance lifecycle, Amazon EC2 Auto Scaling would be more appropriate.

3. If you still prefer the Fleet approach, EC2 Fleet with type "instant" can be used to launch On-Demand Instances and provides more capabilities than the RunInstances API.

Remember that the main benefit of Spot Fleet is the ability to combine On-Demand and Spot Instances to optimize for cost and availability. Using it solely for On-Demand Instances doesn't leverage its key advantages.
Sources
Example CLI configurations Spot Fleet - Amazon Elastic Compute Cloud
Configure an EC2 Fleet of type instant - Amazon Elastic Compute Cloud
Best practices for Amazon EC2 Spot - Amazon Elastic Compute Cloud