Deep Dive into AWS EC2 Spot Instances & Spot Fleets

What Are EC2 Spot Instances?

EC2 Spot Instances allow users to purchase spare AWS compute capacity at discounts of up to 90% compared to On-Demand pricing.

• How Spot Pricing Works:
  • You define a maximum spot price you are willing to pay.
  • If the current spot price is below your max price, you get the instance.
  • If the spot price exceeds your max price, your instance is stopped or terminated (depending on your settings).
  • AWS provides a 2-minute grace period before termination.

Two Termination Strategies for Spot Instances:

1. Stop & Resume:
   • The instance is stopped and can be restarted when the spot price drops again.
   • Ideal for stateful workloads that need to resume processing later.
2. Terminate & Relaunch:
   • The instance is terminated, and a new instance will need to be launched.
   • Suitable for stateless workloads that can start fresh.

Using Spot Blocks for Guaranteed Uptime

If you don't want your spot instance to be interrupted, use a Spot Block:

• Ensures the instance runs without interruption for 1 to 6 hours.
• Rare cases exist where AWS may reclaim the instance, but it's uncommon.

When to Use Spot Instances?

Spot instances are best suited for:

✅ Batch jobs

✅ Data analysis

✅ Fault-tolerant workloads (resilient to interruptions)

They are not recommended for:

❌ Critical applications

❌ Databases or workloads needing persistent storage