Exam AWS Certified SysOps Administrator - Associate topic 1 question 389 discussion

The question states that 12 instances need to be running at all times. In 3 AZ's with 6 instances in each = 18 instances. If you lose 1 AZ, you have instances running.

D. 3 AZs with 6 instances in each AZ. Here's why this solution is optimal: High Availability: Distributing instances across three AZs provides high availability. In the event of a failure in one AZ, the remaining two AZs can continue to serve the application without performance degradation. Load Distribution: With 6 instances in each of the 3 AZs, the application maintains a total of 18 instances. This setup exceeds the minimum requirement of 12 instances, ensuring that even if one AZ fails, there are still 12 instances available (6 in each of the remaining two AZs) to handle the load without performance issues. Fewest Running Instances: This solution provides a balance between high availability and cost-efficiency. It ensures that there are enough instances to handle an AZ failure without unnecessarily doubling the number of instances.

This is math question :)

D running the instance is lower B.

D makes the most sense MAX number is 18, if one AZ drops you have 12 For B: you would have MAX 24, which is more than 18

why not D ? will have max of 18 but will still drop to 12 if one AZ fails

The question is "Which solution will meet the requirements with the fewest running instances possible?", so I go for D with 3 AZ and 6 instances, as we than have the maximum of 18 instances, instead with 2 AZs and 12 instances which would equal to maximum 24 instances.

the application must maintain a minimum of 12 instances at all times. it means that 12 per available zone. B is correct.

B. 2 AZs with 12 instances in each AZ This configuration provides redundancy across two AZs and meets the minimum instance requirement. In the event of an AZ failure, the other AZ can handle the load. Option A (2 AZs with 6 instances in each AZ) does not meet the minimum instance requirement during an AZ failure, and options C and D distribute the instances across three AZs, which might lead to more running instances than necessary.