SOA-C02 Application Load Balancer (ALB) Practice Question
A company runs a stateless web application on Amazon EC2 instances in an Auto Scaling group across two Availability Zones. The SysOps administrator needs to ensure that the application can tolerate a failure of an entire Availability Zone. Which configuration is required?
⚠ Common exam trap
Watch out — candidates often confuse high availability with data durability or instance protection, leading them to choose termination protection or Elastic IPs, when the core requirement is automatic traffic rerouting across AZs, which only a load balancer with health checks can provide.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use an Application Load Balancer (ALB) that spans both Availability Zones with health checks enabled.
An Application Load Balancer (ALB) that spans both Availability Zones with health checks enabled distributes incoming traffic across EC2 instances in multiple AZs. If an entire AZ fails, the ALB automatically routes traffic only to healthy instances in the remaining AZ, ensuring the stateless web application remains available. Health checks detect instance or AZ failure and remove unhealthy targets from the load balancer's target group, which is essential for fault tolerance.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use an Application Load Balancer (ALB) that spans both Availability Zones with health checks enabled.
Why this is correct
An Application Load Balancer (ALB) is a regional service that spans all Availability Zones (AZs) in its subnet configuration and actively sends health-check requests to each registered target. When an EC2 instance or an entire AZ fails health checks, the ALB automatically stops routing new traffic to that target and continues serving requests from healthy instances in other AZs. Coupled with an Auto Scaling group that spans multiple AZs, this design provides both elasticity and zone-failure tolerance, because the ALB constantly updates its target membership based on instance health and scaling events.
- ✗
Enable termination protection on all Amazon EC2 instances.
Why it's wrong here
Termination protection is an EC2-level attribute that merely blocks accidental 'terminate' API calls from the console, CLI, or SDK; it does not affect instance status, health checks, or network reachability. If an Availability Zone goes down, all instances inside that zone lose power and networking, and termination protection cannot bring them back or reroute traffic. This option only addresses human error, not infrastructure failures, so it offers no high-availability benefit for multi-AZ resilience.
- ✗
Place the Amazon EC2 instances in a cluster placement group.
Why it's wrong here
A cluster placement group can only be launched within a single Availability Zone because it is designed to pack instances close together for low latency and high-bandwidth inter-instance communication, typically for HPC or tightly coupled workloads. By placing all EC2 instances in one AZ, you actually reduce fault tolerance: if that AZ fails, every instance in the group becomes unavailable simultaneously. Therefore, instead of improving high availability, this option creates a single point of failure.
- ✗
Associate an Elastic IP address with the primary instance.
Why it's wrong here
An Elastic IP address is a static public IPv4 address associated with exactly one instance at a time; if that instance's AZ fails, the instance is unreachable and the EIP itself does nothing to fail over. You could manually reassociate the EIP to another running instance, but that is an operational action requiring intervention and does not provide automatic, transparent recovery. Additionally, for a stateless web application fronted by a load balancer, EIPs are unnecessary because traffic should go through the ALB's DNS name rather than a fixed IP.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SOA-C02 practice question is part of Courseiva's free Amazon Web Services certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the SOA-C02 exam.