SOA-C02 Reliability and Business Continuity Practice Question
A company runs a critical application on EC2 instances in an Auto Scaling group with a minimum of 2 instances. The instances are in a single Availability Zone. The company wants to achieve 99.99% availability. Which change should they make?
⚠ Common exam trap
The trap here is that candidates often focus on increasing instance count or scaling metrics, overlooking that 99.99% availability requires geographic redundancy across Availability Zones, not just more instances in a single zone.
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
✓
Modify the Auto Scaling group to launch instances in multiple Availability Zones and place an Application Load Balancer in front.
To achieve 99.99% availability, the application must survive an Availability Zone (AZ) failure. Running instances in a single AZ creates a single point of failure. By modifying the Auto Scaling group to launch instances in multiple AZs and placing an Application Load Balancer (ALB) in front, traffic is automatically distributed across healthy instances in different AZs, ensuring fault tolerance even if an entire AZ becomes unavailable.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Modify the Auto Scaling group to launch instances in multiple Availability Zones and place an Application Load Balancer in front.
Why this is correct
By distributing instances across multiple Availability Zones and using an Application Load Balancer to route traffic, the application can withstand an entire AZ failure because the remaining AZs continue serving. The ALB performs health checks and only forwards requests to healthy registered targets, automatically shifting load away from failed AZs. This is the core high-availability design for EC2-based architectures.
- ✗
Increase the minimum size of the Auto Scaling group to 4 instances.
Why it's wrong here
Even if you increase the Auto Scaling group's minimum capacity to four instances, all of those instances will still be provisioned within the same single Availability Zone if the group is configured for only one AZ. An outage or network failure affecting that AZ will take all four instances offline simultaneously, so increasing instance count does not introduce any fault isolation. Availability requires spreading resources across independent AZs, not simply adding more instances in the same location.
- ✗
Use a larger EC2 instance type to handle more traffic.
Why it's wrong here
Scaling up to a larger EC2 instance type (e.g., from m5.large to m5.4xlarge) only adds more compute, memory, and network capacity to a single instance. It does absolutely nothing to eliminate the single point of failure created by running your application in one Availability Zone; if that AZ goes down, the larger instance is just as unreachable as a smaller one. Vertical scaling addresses performance bottlenecks, not availability.
- ✗
Configure the Auto Scaling group to scale based on memory utilization.
Why it's wrong here
A memory-utilization-based scaling policy tells the Auto Scaling group to add or remove instances based on the group's aggregate memory pressure. While this can help maintain consistent performance during load spikes, it does not change where the instances are placed; if the group is confined to one AZ, all instances remain vulnerable to the failure of that AZ. Scaling policies influence capacity, not fault tolerance or geographic distribution.
Go deeper
Related to this question
About these practice questions
Courseiva writes every SOA-C02 question from scratch — 1,169 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
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.