Step-by-Step Explanation:

Understand the Problem:

The company has a stateless application on 10 EC2 On-Demand Instances in an Auto Scaling group.

At least 6 instances are needed to meet service requirements.

The goal is to maintain uptime cost-effectively.

Analyze the Requirements:

Maintain a minimum of 6 instances to meet service requirements.

Optimize costs by using a mix of instance types.

Evaluate the Options:

Option A: Use a Spot Fleet with an On-Demand capacity of 6 instances.

Spot Fleets allow you to request a combination of On-Demand and Spot Instances.

Ensuring a minimum of 6 On-Demand Instances guarantees the required capacity while leveraging lower-cost Spot Instances to meet additional demand.

Option B: Update the Auto Scaling group with a minimum of 6 On-Demand Instances and a maximum of 10 On-Demand Instances.

This option ensures the minimum required capacity but does not optimize costs since it only uses On-Demand Instances.

Option C: Update the Auto Scaling group with a minimum of 1 On-Demand Instance and a maximum of 6 On-Demand Instances.

This does not meet the requirement of maintaining at least 6 instances at all times.

Option D: Use a Spot Fleet with a target capacity of 6 instances.

This option relies entirely on Spot Instances, which may not always be available, risking insufficient capacity.

Select the Best Solution:

Option A: Using a Spot Fleet with an On-Demand capacity of 6 instances ensures the necessary uptime with a cost-effective mix of On-Demand and Spot Instances.

Amazon EC2 Auto Scaling

Amazon EC2 Spot Instances

Spot Fleet Documentation

Using a Spot Fleet with a combination of On-Demand and Spot Instances offers a cost-effective solution while ensuring the required minimum capacity for the application.