SOA-C02 Networking and Content Delivery Practice Question
Which TWO actions should a SysOps administrator take to improve the availability and reduce latency for a web application hosted on EC2 instances behind an Application Load Balancer?
⚠ Common exam trap
Watch out — candidates often confuse vertical scaling (larger instances) with horizontal scaling (more instances across AZs), or they mistakenly think that reducing health check intervals always improves availability, when in fact it can cause flapping and reduce stability.
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
✓
Implement Auto Scaling to add instances based on CPU utilization.
Auto Scaling based on CPU utilization dynamically adjusts the number of EC2 instances to match demand, improving availability by ensuring sufficient capacity during traffic spikes and reducing latency by distributing load across more instances. Option E is correct because deploying EC2 instances in multiple Availability Zones (AZs) provides fault tolerance: if one AZ fails, the ALB continues routing traffic to healthy instances in other AZs, which also reduces latency by serving users from the closest AZ.
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 larger EC2 instance types to handle more traffic.
Why it's wrong here
Scaling up to larger instance types increases the compute capacity of a single server, but it does not remove the dependency on that one instance. If the instance fails, the ALB still has no healthy target to route traffic to, and the entire application becomes unavailable. Vertical scaling also reaches practical limits and is more expensive per unit of capacity, whereas horizontal scaling across multiple instances provides both resilience and elasticity.
- ✗
Configure the ALB health check to have a shorter interval.
Why it's wrong here
Shortening the ALB health check interval allows the load balancer to detect and deregister an unhealthy EC2 instance more quickly, reducing the window of requests routed to a failed target. However, this is a reactive measure: it does nothing to prevent the underlying instance failure or to absorb sudden increases in traffic. It also risks marking instances unhealthy due to transient latency spikes, potentially causing unnecessary instance replacement cycles.
- ✗
Use an Amazon CloudFront distribution in front of the ALB to cache content at edge locations.
Why it's wrong here
Placing a CloudFront distribution in front of the ALB can reduce latency for static assets by serving them from edge locations and offloads some traffic from the origin. But for dynamic or uncached requests, CloudFront must still forward to the ALB, and it does not add resilience to the ALB or EC2 instances themselves. If the origin becomes unreachable or an AZ fails, CloudFront alone cannot keep the application available because it cannot fail over to a healthy origin on its own.
- ✓
Implement Auto Scaling to add instances based on CPU utilization.
Why this is correct
Implementing Auto Scaling with a CPU utilization-based policy enables the fleet to add instances during demand spikes and remove them when load drops, which distributes the request load across more targets and reduces response time. This horizontal elasticity directly addresses latency and performance constraints by expanding capacity in an automated and predictable way. Combined with multi-AZ deployment, it also provides a self-healing, resilient architecture, but its primary benefit here is maintaining performance under changing load.
- ✓
Deploy EC2 instances in multiple Availability Zones.
Why this is correct
Launching EC2 instances across multiple Availability Zones ensures that the application can survive the failure of an entire data center or AZ, because the ALB continues to route traffic to healthy instances in the remaining zones. This design eliminates a single point of failure and is a fundamental requirement for building highly available workloads on AWS. Without multi-AZ redundancy, even a perfectly scalable Auto Scaling group is vulnerable if all of its instances reside in a single AZ that fails.
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Same concept, more angles
2 more ways this is tested on SOA-C02
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which TWO actions can a SysOps administrator take to improve the availability of a web application using an Application Load Balancer (ALB) and EC2 instances? (Choose two.)
medium- A.Place all instances in a single subnet to reduce latency
- ✓ B.Configure health checks on the target group
- ✓ C.Deploy EC2 instances in multiple Availability Zones
- D.Use larger instance types to handle more traffic
- E.Increase the deregistration delay (connection draining) timeout
Why B: Health checks allow the ALB to automatically detect unhealthy EC2 instances and stop routing traffic to them, which prevents failed requests from reaching users. By configuring health checks on the target group, the ALB can mark instances as unhealthy based on criteria like HTTP response codes or timeout thresholds, and then route traffic only to healthy instances. This directly improves availability by ensuring that requests are not sent to failed or degraded instances.
Variation 2. Which TWO actions can be taken to improve the availability of a web application hosted on EC2 instances behind an Application Load Balancer? (Select two.)
medium- ✓ A.Configure an Auto Scaling group with health checks to replace unhealthy instances.
- B.Use larger EC2 instance types.
- ✓ C.Deploy the EC2 instances across multiple Availability Zones.
- D.Use a single AWS Region for all instances.
- E.Place all EC2 instances in a single subnet.
Why A: Option A is correct because an Auto Scaling group configured with health checks (ELB or EC2 health checks) automatically detects and replaces unhealthy instances, maintaining the desired capacity and thus improving availability. Option C is correct because deploying EC2 instances across multiple Availability Zones provides fault isolation; if one AZ fails, the Application Load Balancer routes traffic to healthy instances in other AZs, maintaining availability. Option B is incorrect because larger instance types increase capacity/performance but do not address redundancy or failure recovery. Option D is incorrect because using a single Region does not improve availability against AZ-level failures and is not a redundancy measure. Option E is incorrect because placing all instances in a single subnet concentrates them in one AZ, reducing availability and creating a single point of failure.
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.