How to Use Spot Instances for Savings in AWS

Use AWS Spot Instances to save up to 90% on compute costs by running workloads on spare EC2 capacity. Launch Spot Instances via the AWS Management Console, AWS CLI, or CloudFormation, and design your applications to handle interruptions gracefully.

Syntax

To request a Spot Instance, you specify the instance type, maximum price, and launch parameters. You can do this using the AWS CLI or SDKs.

Key parts:

• InstanceType: The type of EC2 instance you want.
• SpotPrice: The max price you are willing to pay per hour.
• LaunchSpecification: Details like AMI ID, key pair, security groups.

bash

aws ec2 request-spot-instances \
  --spot-price "0.05" \
  --instance-count 1 \
  --type "one-time" \
  --launch-specification '{"ImageId":"ami-0abcdef1234567890","InstanceType":"t3.micro","KeyName":"my-key","SecurityGroups":["default"]}'

Example

This example shows how to request a Spot Instance using AWS CLI with a maximum price of $0.03 per hour for a t3.micro instance. It demonstrates launching a one-time Spot Instance with a specified AMI and security group.

bash

aws ec2 request-spot-instances \
  --spot-price "0.03" \
  --instance-count 1 \
  --type "one-time" \
  --launch-specification '{"ImageId":"ami-0abcdef1234567890","InstanceType":"t3.micro","KeyName":"my-key","SecurityGroups":["default"]}'

Output

{
  "SpotInstanceRequests": [
    {
      "SpotInstanceRequestId": "sir-12345678",
      "State": "open",
      "Status": {
        "Code": "pending-evaluation",
        "Message": "Your Spot request is being evaluated."
      }
    }
  ]
}

Common Pitfalls

Common mistakes when using Spot Instances include:

• Not designing applications to handle sudden interruptions, which can cause data loss.
• Setting a Spot price too low, causing requests to remain unfulfilled.
• Using Spot Instances for critical workloads without fallback options.
• Ignoring the Spot Instance interruption notices that AWS provides.

Always combine Spot Instances with On-Demand or Reserved Instances for reliability.

bash

## Wrong: Using Spot Instances for critical database without backup
# This can cause data loss if instance is terminated suddenly.

## Right: Use Spot Instances for batch jobs or stateless apps
# and save state frequently or use persistent storage like EBS or S3.

Quick Reference

Concept	Description
Spot Instance	EC2 instance using spare AWS capacity at discounted price.
Spot Price	Maximum hourly price you agree to pay for Spot Instance.
Interruption	AWS can terminate Spot Instances with 2-minute warning.
Use Cases	Batch jobs, stateless apps, flexible workloads.
Fallback	Combine with On-Demand or Reserved Instances for reliability.

Key Takeaways

Spot Instances offer up to 90% savings by using spare AWS capacity.

Design your apps to handle interruptions gracefully to avoid data loss.

Set a realistic Spot price to increase chances of instance fulfillment.

Use Spot Instances for flexible, non-critical workloads.

Combine Spot with On-Demand or Reserved Instances for reliability.