Questions 4 to 6

Explanations for questions 4 to 6

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Question 4

A retail organization sends coupons out twice a week, and this results in a predictable surge in sales traffic. The application runs on Amazon EC2 instances behind an Elastic Load Balancer. The organization is looking for ways to reduce costs without impacting performance or reliability. How can they achieve this goal?

  1. Purchase scheduled reserved instances.
  2. Use a mixture of spot instances and on-demand instances.
  3. Increase the instance size of the existing EC2 instances.
  4. Purchase Amazon EC2 dedicated hosts.

Correct Answer: 1

Explanation: Scheduled reserved instances (scheduled instances) enable you to purchase capacity reservations that recur on a daily, weekly, or monthly basis, with a specified start time and duration, for a one-year term. You reserve the capacity in advance so that you know it is available when you need it. You pay for the time that the instances are scheduled, even if you do not use them.

Scheduled instances are a good choice for workloads that do not run continuously but do run on a regular schedule. For example, you can use scheduled instances for an application that runs during business hours or for batch processing that runs at the end of the week.

CORRECT: “Purchase scheduled reserved instances.” is the correct answer.

INCORRECT: “Use a mixture of spot instances and on-demand instances.” is incorrect. You can mix spot and on-demand in an Auto Scaling group. However, there’s a risk the spot price may not be good, and as this is a regular, predictable increase in traffic, a scheduled reserved instance is a safer option.

INCORRECT: “Increase the instance size of the existing EC2 instances.” is incorrect. This would add more cost all of the time rather than catering for the temporary increase in traffic.

INCORRECT: “Purchase Amazon EC2 dedicated hosts.” is incorrect. This is not a way to be cost efficient as dedicated hosts are much more expensive than shared hosts.


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