Question 671 of 247
Improving Availability with ALB and EC2
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.)
Quick Answer
The correct actions to improve availability are deploying EC2 instances across multiple Availability Zones and using an Auto Scaling group to replace unhealthy instances. Distributing instances across multiple Availability Zones eliminates a single point of failure by ensuring that if one zone goes down, the Application Load Balancer can route traffic to healthy instances in another zone. An Auto Scaling group automatically replaces failed or unhealthy instances, maintaining the desired capacity and further enhancing fault tolerance. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this question tests your understanding of high-availability architecture patterns, often with traps like choosing a single subnet or a larger instance type—both of which improve performance or simplicity, not availability. A common memory tip is to remember that availability comes from redundancy across zones and automated recovery, not from bigger or fewer resources. Think “spread and replace” to recall the two key actions.
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 health checks to replace unhealthy instances.
An Auto Scaling group with health checks can automatically replace unhealthy EC2 instances, improving availability. Option C is correct because deploying instances across multiple Availability Zones provides fault tolerance; if one AZ fails, your application continues to run in another. Option B is incorrect because using larger instance types improves performance, not availability. Option D is incorrect because using a single region makes the application vulnerable to region-wide failures, reducing availability. Option E is incorrect because placing all instances in a single subnet creates a single point of failure; distributing across AZs is necessary for high availability.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Configure an Auto Scaling group with health checks to replace unhealthy instances.
Why this is correct
Auto Scaling automatically replaces unhealthy instances.
- ✗
Use larger EC2 instance types.
Why it's wrong here
Larger instances improve performance, not availability.
- ✓
Deploy the EC2 instances across multiple Availability Zones.
Why this is correct
Multi-AZ deployment protects against AZ failures.
- ✗
Use a single AWS Region for all instances.
Why it's wrong here
Single region does not provide regional fault tolerance.
- ✗
Place all EC2 instances in a single subnet.
Why it's wrong here
Single subnet is a single point of failure.
Visual reference
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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 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?
medium- A.Use larger EC2 instance types to handle more traffic.
- B.Configure the ALB health check to have a shorter interval.
- C.Use an Amazon CloudFront distribution in front of the ALB to cache content at edge locations.
- ✓ D.Implement Auto Scaling to add instances based on CPU utilization.
- ✓ E.Deploy EC2 instances in multiple Availability Zones.
Why D: 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.
Last reviewed: Jun 20, 2026
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