SOA-C02 Reliability and Business Continuity Practice Question
A company runs a web application on Amazon EC2 instances in a single Availability Zone. The SysOps administrator wants to increase the availability of the application so that it can survive an Availability Zone failure. Which action is the most effective?
⚠ Common exam trap
Test-takers frequently confuse high availability with fault tolerance at a single component level, mistakenly thinking that adding more instances in the same AZ or enabling termination protection improves availability, when in fact only distributing resources across multiple isolated Availability Zones can survive an AZ failure.
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
✓
Launch EC2 instances in two different Availability Zones and place them behind an Application Load Balancer.
Deploying EC2 instances across two different Availability Zones and placing them behind an Application Load Balancer (ALB) provides fault isolation. If one AZ fails, the ALB automatically routes traffic to the healthy instances in the other AZ, ensuring the application remains available. This architecture directly addresses the goal of surviving an AZ failure by eliminating the single point of failure at the AZ level.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Deploy an additional EC2 instance in the same Availability Zone.
Why it's wrong here
Adding an EC2 instance within the same Availability Zone does not create fault-domain redundancy because an AZ is a single failure domain—if the AZ goes down, all instances in it become unreachable. The new instance would not serve traffic independently unless it is behind a load balancer or has a data replication and failover mechanism, and even then a same-AZ placement adds no resilience against an AZ failure. This option only increases capacity, not availability.
- ✓
Launch EC2 instances in two different Availability Zones and place them behind an Application Load Balancer.
Why this is correct
Launching EC2 instances in two different Availability Zones and placing them behind an Application Load Balancer is the canonical web-tier high availability pattern. The ALB performs continuous health checks and distributes traffic to healthy targets across both AZs. If an entire AZ becomes unhealthy, the ALB automatically reroutes requests to instances in the remaining AZ, preserving the application's availability. This design eliminates the AZ as a single point of failure for the web tier.
- ✗
Enable termination protection on all EC2 instances.
Why it's wrong here
Termination protection is a data-loss safeguard that prevents users or scripts from accidentally terminating an EC2 instance; it does not affect the instance's runtime health or its ability to withstand infrastructure failures. An instance can still be lost due to an underlying hardware degradation or an Availability Zone outage, and termination protection will not trigger or contribute to failover. Therefore it provides no availability benefit for the application as a whole.
- ✗
Use an Amazon RDS Multi-AZ deployment for the database tier.
Why it's wrong here
Deploying Amazon RDS Multi-AZ improves the database tier's resilience by automatically failing over to a standby replica in a different AZ, but it does not make the web application tier itself redundant. The question specifically concerns the EC2 web instances, which would remain a single point of failure if they are confined to one AZ or lack a load balancer. Even with a highly available database, the application still goes down if its only web server fails, so this option does not address the application tier's availability requirement.
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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.