Which solution will meet the requirements with the fewest running instances possible?

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In: SOA-C02
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With: 1 Comment
A company’s web application runs on Amazon EC2 instances in a single AWS Region.The infrastructure must be designed so the application remains available with no performance degradation in the event of an Availability Zone (AZ) failure.To ensure optimal performance, the application must maintain a minimum of 12 instances at all times.

Which solution will meet the requirements with the fewest running instances possible?

2 AZs with 6 instances in each AZ

2 AZs with 12 instances in each AZ

3 AZs with 4 instances in each AZ

3 AZs with 6 instances in each AZ

Explanations:

If 6 instances are deployed in each of the 2 AZs, a failure of one AZ would leave only 6 instances running, which is below the required minimum of 12 instances.

Although there would be a total of 24 instances (12 in each AZ), this option is not optimal as it exceeds the minimum required instances, leading to unnecessary costs while not providing the least running instances.

With 4 instances in each of the 3 AZs, a failure of one AZ would leave only 8 instances running, which does not meet the requirement of maintaining at least 12 instances.

This option provides 6 instances in each of the 3 AZs, resulting in a total of 18 instances. If one AZ fails, there would still be 12 instances running, meeting the requirements with the fewest instances possible.

2025-10-09

1 Comment

  1. Christine
    Author

    I judge that the answer is:
    3 AZs with 6 instances in each AZ

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