SOA-C02 Reliability and Business Continuity Practice Question
A company is designing a highly available architecture for a web application. The application uses an Application Load Balancer (ALB) and an Auto Scaling group of EC2 instances. Which TWO steps should the company take to ensure the architecture is resilient to an Availability Zone failure? (Select TWO.)
⚠ Common exam trap
Watch out — candidates often confuse scaling capacity (Option A) or monitoring (Option B) with the architectural requirement of distributing resources across multiple Availability Zones, which is the only way to 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
✓
Configure the Auto Scaling group to launch instances in at least two Availability Zones.
Launching EC2 instances in at least two Availability Zones (AZs) ensures that if one AZ fails, the Auto Scaling group can continue to serve traffic from instances in the remaining AZ(s). This is a fundamental design pattern for high availability within a single AWS Region, as it distributes the application across physically separate data centers.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Set the Auto Scaling group's desired capacity to a high number.
Why it's wrong here
High capacity in one AZ does not protect against AZ failure.
- ✗
Create a CloudWatch alarm that triggers if the ALB has elevated 5xx errors.
Why it's wrong here
Alarms detect issues but do not prevent AZ failure impact.
- ✓
Configure the Auto Scaling group to launch instances in at least two Availability Zones.
Why this is correct
Distributing instances across AZs ensures availability if one AZ fails.
- ✗
Use a single EC2 instance type for all instances.
Why it's wrong here
Instance type does not affect AZ resilience.
- ✓
Configure the ALB to be internet-facing and enable cross-zone load balancing.
Why this is correct
Cross-zone load balancing allows the ALB to distribute traffic across instances in multiple AZs.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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