5-Minute Read: AWS Spot Instance Pricing FAQ
As per AWS documentation, with Spot instances, you pay the Spot price that’s in effect for the time period your instances are running. Spot instance prices are set by Amazon EC2 and adjust gradually based on long-term trends in supply and demand for Spot instance capacity.
Here are some quick exercises and Q&A snippets taken from our AWS Certified Solutions Architect Associate Practice test course.
What price will I pay for a Spot instance?
A: You pay the Spot price that’s in effect at the beginning of each instance-hour for your running instance. If Spot price changes after you launch the instance, the new price is charged against the instance usage for the subsequent hour.
How am I charged if Spot price changes while my instance is running?
A: You will pay the price per instance-hour set at the beginning of each instance-hour for the entire hour, billed to the nearest second.
Here is another scenario question covering Spot instance pricing:
You have acquired a new EC2 Spot Instance at a bid price of $0.03/hr. However, the Spot price increases to $0.05/hr after 40 minutes. What was the total EC2 compute cost of running your Spot Instance for that hour?
Correct Answer is Option 4 – $0.
If your Spot instance is terminated or stopped by Amazon EC2 in the first instance hour, you will not be charged for that usage. However, if you terminate the instance yourself, you will be charged to the nearest second. If the Spot instance is terminated or stopped by Amazon EC2 in any subsequent hour, you will be charged for your usage to the nearest second. If you are running on Windows and you terminate the instance yourself, you will be charged for an entire hour.
For more helpful practice exercises like this, check out our best selling AWS Solutions Architect practice test course here.
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