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By: CloudUtil Latest Version: 1.0.8

Product Overview

Interested to save up to 90% of your EC2 instance costs? Read on!

Let's start with a bit of introduction to the main concepts:

What are EC2 instances?

EC2 instances are computers or virtual machines that you can rent by the second from a cloud provider.

What are Spot instances?

Spot instances are spare EC2 capacity, made available at a steep discount of up to 90% lower than the usual on-demand cost of EC2 instances.

The only difference is that they can be claimed back with at least 2 minutes (typically 5-15min) notice when EC2 may need the capacity for other on-demand customers.

In average only about 5% of the Spot instances get interrupted in their first month of usage, and these interruptions can usually be handled automatically.

Would Spot be a good fit for my application?

Many cloud-native workloads are already resilient to such interruptions, as they satisfy a few key criteria:

  1. redundancy: running on multiple instances from an AutoScaling group so that they can sustain the failure of a single instance without any visible impact
  2. stateless operation, or if stateful and their state can be checkpointed externally or re-created quickly in case of interruptions
  3. start quickly on new instances, preferably in less than 5 minutes
  4. processing happens quickly so that new tasks can be migrated to new instances and old tasks can complete within the termination notice period
  5. support running on multiple similar instance types, across generations and families

Some classic examples include:

  • Applications running in AutoScaling groups, especially if they scale in/out often and safely handle such instance churn
  • Stateless web servers
  • Applications running in Docker containers or from baked AMIs
  • Applications that process data from SQS queues

What does AutoSpotting do?

AutoSpotting allows you to quickly migrate AutoScaling groups to Spot instances.

It's designed towards reducing the adoption effort as much as possible by not requiring launch template/configuration changes, which can be challenging to perform at scale.

All you need to do is to install it from CloudFormation(it takes about 5 minutes) and tag your AutoScaling groups with with Key="spot-enabled" Value="true".

How does AutoSpotting work?

It runs in your AWS account and is subscribed to certain EC2 events across all the enabled AWS regions.

Once a new on-demand instance has been launched in an enabled AutoScaling group, it performs the following actions:

  • launches an identically configured but cheaper Spot instance from the same or a similar instance type
  • swaps this new Spot instance with the On-Demand instance
  • cleanly terminates the On-Demand instance, usually before it even had the chance to boot

The Spot instances will be configured from the start as part of the group, and the group will continuously monitor them as it would monitor any other instances.

This process requires no launch configuration changes on your AutoScaling groups and can be deployed at any scale throughout your infrastructure, allowing to reduce costs tremendously.

You can also configure AutoSpotting to only replace a percentage of each AutoScaling group to Spot, which is often desirable in production environments.

Many customers install AutoSpotting on hundreds of AWS accounts and empower their teams to enable it on a per-group basis by simply tagging their AutoScaling groups as mentioned above, without the need to configure the instance types needed for each group, which can be tedious on large organizations.

Some customers even run it in opt-out mode, which takes over all the AutoScaling groups unless they are tagged with Key="spot-enabled" Value="false", a very convenient way to quickly migrate to Spot, especially when combined with the option to keep a percentage of On-Demand instances.

How much can it save?

This heavily depends on your configuration, and on how many groups it can be enabled.

The average savings are around 70-75% of the on-demand prices, significantly more than you can achieve with Reserved Instances or Savings plans, and without any time commitments.

How much does it cost?

AutoSpotting costs less than 5% of the savings it generates over on-demand.

You're charged hourly in increments of $0.001 for each $0.02/hour it saved you.

It is free of charge if it saves you less than $0.02/hour and also for the partial amounts up to the next multiple of $0.02/hour.

Monthly this becomes $0.73 for each $14.6 saved by using it, considering 730 hours/month.

For example if it saves you $40 you'll get charged only $1.46 monthly (for the first $29.2 it saved you), and so on.

When it comes to operational costs, it has negligible runtime costs due to its serverless implementation and it also doesn't require ongoing maintenance.

For further information please refer to the documentation available at



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