Reply To: Spot instance is not a guaranteed instance type

[Tutorials-Dojo]

Hi,

I understand your point but it is clearly mentioned in the AWS documentation that Spot Instances can be used for handling the peak load or peak traffic of your web application.

“Maintain optimal web performance during peak traffic at low costs using Spot Instances…”

https://aws.amazon.com/ec2/spot/?cards.sort-by=item.additionalFields.startDateTime&cards.sort-order=asc

Spot Fleets are also used to provide a certain level of availability to your applications: https://aws.amazon.com/blogs/compute/running-web-applications-on-amazon-ec2-spot-instances/

Moreover, a Spot Fleet can deploy different EC2 instances across different Availability Zones, and not just a single AZ. This strengthens its compatibility for the explicit requirement in the scenario that says:

“…to recover quickly in the event that an Availability Zone is unavailable during peak load? “

Take note that the scenario explicitly asks for the cost-effective option. That’s the primary keyword here, and again, the overall availability of the application isn’t compromised.

You have a point that there would be several requests that would be affected when the Spot Instances got interrupted by AWS. That’s an edge case scenario and if you chose On-Demand/Reserved Instance simply based on this “edge-case”, then you are ignoring the primary keyword that focuses on cost. Doing so will make you fail the exam as AWS won’t add an important keyword at the bottom of the scenario that isn’t related to the answer it expects.

The SA Pro exam is a difficult test because you have to weigh in these different considerations on your architecture. We can’t be too obsessed with application availability if the scenario explicitly mentioned focusing on cost, especially if there’s already a provision for availability in terms of a Spot Fleet with a diversified allocation strategy solution.

If the web application is stateless and can handle the request failures through retries, then it shouldn’t be a problem. Spot Instances have 2-minute notification too before it gets terminated.

I’ve passed 10 AWS Certifications and in my opinion, if there are 2 explicit key phrases in the scenario that points to a particular AWS Service, then AWS considers that as the correct answer and not the minor details in the scenario.

Regards,

Jon Bonso