Spot instances enable you to bid on unused EC2 instances, which can lower your Amazon EC2 costs significantly. The hourly price for a Spot instance (of each instance type in each Availability Zone) is set by Amazon EC2, and fluctuates depending on the supply of and demand for Spot instances. Your Spot instance runs whenever your bid exceeds the current market price.
Spot instances are a cost-effective choice if you can be flexible about when your applications run and if your applications can be interrupted. For example, Spot instances are well-suited for data analysis, batch jobs, background processing, and optional tasks. For more information, see Amazon EC2 Spot Instances.
The key differences between Spot instances and On-Demand instances are that Spot instances might not start immediately, the hourly price for Spot instances varies based on demand, and Amazon EC2 can terminate an individual Spot instance as the hourly price for or availability of Spot instances changes. One strategy is to launch a core group of On-Demand instances to maintain a minimum level of guaranteed compute resources for your applications, and supplement them with Spot instances when the opportunity arises.
Another strategy is to launch Spot instances with a required duration (also known as Spot blocks), which are not interrupted due to changes in the Spot price. For more information, see Specifying a Duration for Your Spot Instances.
Before you get started with Spot instances, you should be familiar with the following concepts:
Spot instance pool—A set of unused EC2 instances with the same instance type, operating system, Availability Zone, and network platform (EC2-Classic or EC2-VPC).
Spot price—The current market price of a Spot instance per hour, which is set by Amazon EC2 based on the last fulfilled bid. You can also retrieve the Spot price history.
Spot instance request (or Spot bid)—Provides the maximum price (bid price) that you are willing to pay per hour for a Spot instance. When your bid price exceeds the Spot price, Amazon EC2 fulfills your request. Note that a Spot instance request is either one-time or persistent. Amazon EC2 automatically resubmits a persistent Spot request after the Spot instance associated with the request is terminated. Your Spot instance request can optionally specify a duration for the Spot instances.
Spot fleet—A set of Spot instances that is launched based on criteria that you specify. The Spot fleet selects the Spot instance pools that meet your needs and launches Spot instances to meet the target capacity for the fleet. The Spot fleet also maintains the target capacity of the fleet over time by launching replacement instances after Spot instances in the fleet are terminated.
Spot instance interruption—Amazon EC2 terminates your Spot instance when the Spot price exceeds your bid price or there are no longer any unused EC2 instances. Amazon EC2 marks the Spot instance for termination and provides a Spot instance termination notice, which gives the instance a two-minute warning before it terminates.
Bid status—Provides detailed information about the current state of your Spot bid.
How to Get Started
The first thing you need to do is get set up to use Amazon EC2. It can also be helpful to have experience launching On-Demand instances before launching Spot instances.
Working with Spot Instances
You can provision Spot instances directly using Amazon EC2. You can also provision Spot instances using other services in AWS. For more information, see the following documentation.
- Auto Scaling and Spot instances
You can create launch configurations with a bid price so that Auto Scaling can launch Spot instances. For more information, see Launching Spot instances in Your Auto Scaling Group in the Auto Scaling User Guide.
- Amazon EMR and Spot instances
There are scenarios where it can be useful to run Spot instances in an Amazon EMR cluster. For more information, see Lower Costs with Spot Instances in the Amazon Elastic MapReduce Developer Guide.
- AWS CloudFormation Templates
AWS CloudFormation enables you to create and manage a collection of AWS resources using a template in JSON format. AWS CloudFormation templates can include a Spot price. For more information, see EC2 Spot Instance Updates - Auto Scaling and CloudFormation Integration.
- AWS SDK for Java
You can use the Java programming language to manage your Spot instances. For more information, see Tutorial: Amazon EC2 Spot Instances and Tutorial: Advanced Amazon EC2 Spot Request Management.
- AWS SDK for .NET
You can use the .NET programming environment to manage your Spot instances. For more information, see Tutorial: Amazon EC2 Spot instances.
You pay the Spot price for Spot instances, which is set by Amazon EC2 and fluctuates periodically depending on the supply of and demand for Spot instances. If your bid price exceeds the current Spot price, Amazon EC2 fulfills your request and your Spot instances run until either you terminate them or the Spot price increases above your bid price.
Everyone pays that same Spot price for that period, regardless of whether their bid price was higher. You never pay more than your bid price per hour, and often pay less per hour. For example, if you bid $0.25 per hour, and the Spot price is $0.20 per hour, you only pay $0.20 per hour. If the Spot price drops, you pay the new, lower price. If the Spot price rises, you pay the new price if it is equal to or less than your bid price. If the Spot price rises above your bid price, then your Spot instance is interrupted.
At the start of each instance hour, you are billed based on the Spot price. If your Spot instance is interrupted in the middle of an instance hour because the Spot price exceeded your bid, you are not billed for the partial hour of use. If you terminate your Spot instance in the middle of an instance hour, you are billed for the partial hour of use.
Note that Spot instances with a predefined duration use a fixed hourly price that remains in effect for the Spot instance while it runs.
To view the current (updated every five minutes) lowest Spot price per region and instance type, see the Spot Instances Pricing page.
If you have questions concerning AWS billing, accounts, and events, contact AWS Support.