Spot instances provide you with access to unused Amazon EC2 capacity at steep discounts relative to On-Demand prices. The Spot price fluctuates based on the supply and demand of available unused EC2 capacity.
When you request Spot instances, you specify the maximum Spot price you are willing to pay. Your Spot instance is launched when the Spot price is lower than the price you specified, and will continue to run until you choose to terminate it or the Spot price exceeds the maximum price you specified.
With Spot instances, you will never be charged more than the maximum price you specified. While your instance runs, you are charged the Spot price that is in effect for that period. If the Spot price exceeds your specified price, your instance will receive a two-minute notification before it is terminated, and you will not be charged for the partial hour that your instance has run.
If you include a duration requirement with your Spot instances request, your instance will continue to run until you choose to terminate it, or until the specified duration has ended; your instance will not be terminated due to changes in the Spot price.
Spot prices are set by Amazon EC2 and fluctuate periodically depending on the supply of and demand for Spot instance capacity. The following table displays the Spot price for each region and instance type (updated every 5 minutes).
Spot instances are available at a discount of up to 90% compared to On-Demand pricing. To compare the current Spot prices against standard On-Demand rates, visit the Spot Bid Advisor.
Spot instances are also available to run for a predefined duration – in hourly increments up to six hours in length – at a discount of up to 30-50% compared to On-Demand pricing.