Q48 — AWS SOA-C02 Ch.1

Question 48 of 100 | ← Chapter 1

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?

Correct Answer: D. 3 AZs with 6 instances in each AZ

Explanation

AWS最佳实践中，跨多个可用区（AZ）部署资源是确保高可用性的关键。题目要求在单个AZ故障时仍维持至少12个实例，且总实例数最少。若采用3个AZ，每个部署6个实例（选项D），正常情况下总实例数为18。当1个AZ故障时，剩余2个AZ各提供6个实例，总和12，满足最低要求。其他选项中，选项C（3个AZ各4个实例）在AZ故障后仅剩8个实例，不足12；选项A（2个AZ各6个实例）在AZ故障后仅剩6个实例；选项B（2个AZ各12个实例）虽满足条件，但总实例数24多于选项D的18。因此，选项D以最少总实例数满足需求。参考AWS架构良好的框架中对弹性容量和跨AZ冗余的设计原则。