SOA-C02 Reliability and Business Continuity Practice Question
Which TWO actions should a SysOps administrator take to ensure high availability of a web application running on EC2 instances? (Choose two.)
⚠ Common exam trap
A common mix-up: candidates confuse termination protection (a safety feature) with high availability, or think that larger instance types inherently provide fault tolerance, when in fact only redundancy across multiple Availability Zones and automated health-based replacement ensure high availability.
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 an Auto Scaling group with a health check to replace unhealthy instances.
Option D is correct because an Auto Scaling group with health checks (EC2 status checks and optionally ELB health checks) automatically detects and replaces unhealthy instances, maintaining the desired capacity and thus high availability. Option E is correct because deploying EC2 instances across multiple Availability Zones ensures the application survives an AZ-level failure, since each AZ has independent power, cooling, and networking. Option A is incorrect because termination protection only prevents accidental instance termination; it does not improve availability or recover failed instances. Option B is incorrect because placing all instances in a single AZ creates a single point of failure, reducing availability. Option C is incorrect because a larger instance type only increases capacity, not redundancy or 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.
- ✗
Enable termination protection on all EC2 instances.
Why it's wrong here
Termination protection only blocks accidental instance deletion; it does nothing for availability during an AZ or instance failure. It is the right control when guarding against human error or malicious shutdown of a specific instance, not for maintaining service uptime.
- ✗
Launch all EC2 instances in a single Availability Zone.
Why it's wrong here
Concentrating every instance in one Availability Zone means a single AZ outage takes down the whole application, directly contradicting high availability. Single-AZ placement is chosen for lowest inter-instance latency or reduced data transfer costs, not for resilience.
- ✗
Use a larger instance type for all EC2 instances.
Why it's wrong here
A larger instance type increases the capacity of one server but leaves a single point of failure; it does not provide redundancy across hosts or zones. Vertical scaling suits performance or memory bottlenecks, whereas high availability requires horizontal distribution across multiple Availability Zones.
- ✓
Configure an Auto Scaling group with a health check to replace unhealthy instances.
Why this is correct
An Auto Scaling group with health checks continuously monitors instance state and automatically terminates and replaces unhealthy instances, maintaining the desired capacity. This removes failed nodes from service, satisfying the availability requirement without manual intervention.
- ✓
Deploy EC2 instances across multiple Availability Zones.
Why this is correct
Spreading instances across multiple Availability Zones satisfies the high-availability constraint by removing a single-zone failure domain. Each AZ has independent power, cooling and networking, so an outage in one zone leaves instances in other zones serving traffic, provided an Elastic Load Balancer or Route 53 health checks route around the failed zone.
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Variation 1. Which TWO actions improve the availability of an application running on EC2 instances in a single Auto Scaling group? (Choose 2)
medium- ✓ A.Use an Elastic Load Balancer with health checks to route traffic only to healthy instances.
- B.Increase the instance size to handle higher load.
- C.Create a CloudWatch alarm to notify when the CPU utilization exceeds 80%.
- D.Enable EBS optimization on the instances.
- ✓ E.Configure the Auto Scaling group to launch instances in multiple Availability Zones.
Why A: An Elastic Load Balancer (ELB) performs health checks against EC2 instances and automatically routes traffic only to instances that pass those checks. If an instance becomes unhealthy, the ELB stops sending traffic to it, preventing user requests from reaching a failing instance and thereby improving application availability.
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.