SOA-C02 Reliability and Business Continuity Practice Question
A SysOps administrator is responsible for an Auto Scaling group that runs a critical application. The administrator wants to ensure that the application can recover from an AZ failure. Which THREE steps should the administrator take? (Choose three.)
⚠ Common exam trap
Many candidates think using a single AZ simplifies management and reduces latency, but they overlook that this creates a critical single point of failure, which is unacceptable for a critical application requiring AZ failure recovery.
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
✓
Place subnets in each Availability Zone used by the Auto Scaling group.
Placing subnets in each Availability Zone (AZ) used by the Auto Scaling group allows the group to launch EC2 instances in multiple AZs, which is essential for fault isolation. If one AZ fails, the Auto Scaling group can still launch and maintain instances in the other AZs, ensuring application availability. Without subnets in each AZ, the Auto Scaling group cannot distribute instances across AZs, defeating the purpose of high availability.
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 EC2 instances in a single Availability Zone to reduce latency.
Why it's wrong here
Reducing latency is not a valid reason to place all EC2 instances in a single Availability Zone. While same-AZ traffic may have lower inter-instance latency, this architecture creates a single point of failure: if that AZ experiences an outage, the entire application becomes unavailable. Latency concerns should be addressed through edge services, routing policies, or regional selection, not by sacrificing the multi-AZ redundancy that Auto Scaling groups are designed to provide.
- ✓
Place subnets in each Availability Zone used by the Auto Scaling group.
Why this is correct
An Auto Scaling group defines which subnets it can launch instances into, and each subnet maps to exactly one Availability Zone. To spread instances across multiple Availability Zones, you must explicitly configure the ASG to include subnets from each of those zones. Without a corresponding subnet in a given AZ, the group cannot place instances there, so omitting subnets limits the group's ability to recover from zone-level failures.
- ✓
Configure the Auto Scaling group to launch instances in at least two Availability Zones.
Why this is correct
Configuring the Auto Scaling group to launch instances in at least two Availability Zones is essential for high availability. If one AZ fails, the group can still maintain its desired capacity in the remaining zones and automatically restart any instances that become unhealthy. This ensures that a single Availability Zone disruption does not take down the entire workload, which aligns with the core purpose of Auto Scaling for resilient architecture.
- ✓
Attach an Application Load Balancer that is enabled for multiple Availability Zones.
Why this is correct
An Application Load Balancer is a regional resource that must be enabled in the same Availability Zones as the Auto Scaling group's instances to route traffic effectively. By enabling multiple AZs, the ALB can continue distributing requests to healthy targets even if an entire AZ becomes unavailable, because it can route to instances in other zones. This complements the ASG's health checks, allowing the load balancer to detect and isolate unhealthy instances while maintaining service availability.
- ✗
Use a single subnet in one Availability Zone to simplify network design.
Why it's wrong here
Using a single subnet in one Availability Zone may simplify the network design, but it undermines the fundamental requirement for high availability. Since a subnet lives entirely within one AZ, all instances launched in that subnet reside in a single zone, making the application vulnerable to any outage affecting that zone. Additionally, a single subnet might exhaust its available IP addresses during scaling events, and it prevents the Auto Scaling group from fulfilling its intended multi-AZ redundancy strategy.
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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.