DOP-C02 Question 132
Select 3Your company runs a mission-critical web application on AWS that requires high availability and resilience. The application is deployed across multiple Availability Zones (AZs) using an Application Load Balancer (ALB) and auto-scaling groups for the backend instances. Recently, there have been sporadic reports of increased latency and failed requests during AZ failures. What steps should you take to ensure resilience and minimize disruptions during future AZ failures?
- A
Enable cross-zone load balancing on the Application Load Balancer.
- B
Increase the number of Auto Scaling Group instances in the remaining AZs upon detecting an AZ failure.
- C
Configure the Auto Scaling Group to span multiple regions instead of multiple AZs.
- D
Implement Elastic Load Balancer health checks to remove unhealthy instances from the ALB target group.
- E
Use Elastic Block Store (EBS) volumes with instance replication across AZs for backend instances.
Show answer and explanation
Correct answers: A, B, D
Explanation
To ensure application resilience during an AZ failure, enabling cross-zone load balancing helps evenly distribute traffic across available instances. Adjusting Auto Scaling Group capacity dynamically ensures sufficient resources are provisioned in the remaining AZs. Additionally, ELB health checks maintain application reliability by removing unhealthy instances. These measures together minimize disruptions and improve application performance during failures.
- A. Correct.
Enabling cross-zone load balancing allows the ALB to distribute traffic evenly across instances in all AZs, even when one AZ fails, thereby improving resilience and reducing latency.
- B. Correct.
Increasing the number of Auto Scaling Group instances in the remaining AZs compensates for lost capacity during an AZ failure and ensures the application remains available and responsive.
- C. Incorrect.
Configuring the Auto Scaling Group to span multiple regions is not recommended for this scenario as it introduces higher latency and complexity. Multi-AZ architecture is sufficient for high availability.
- D. Correct.
Elastic Load Balancer health checks ensure that unhealthy instances are removed from the ALB target group, maintaining smooth traffic distribution and improving application reliability.
- E. Incorrect.
EBS volumes are AZ-specific and do not replicate across AZs. Instance replication with EBS is not natively supported. Instead, consider using Amazon S3 or Amazon RDS Multi-AZ for data resilience.