SOA-C02 Monitoring, Logging, and Remediation Practice Question
A company hosts a web application on multiple EC2 instances behind an Application Load Balancer (ALB). The SysOps administrator receives a report that the application is experiencing intermittent 503 errors. The ALB target group health checks are configured to check the /health endpoint every 30 seconds with a healthy threshold of 2 and an unhealthy threshold of 2. The administrator checks the ALB metrics and notices that the number of healthy hosts occasionally drops to zero. The EC2 instances are normal and the application logs show no errors. What is the most likely cause and solution?
⚠ Common exam trap
Candidates often confuse increasing the health check interval (Option A) with giving more time for the application to respond, when in fact the timeout parameter directly controls how long the ALB waits for a response before marking the check as failed.
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
✓
Increase the health check timeout to 10 seconds.
The intermittent 503 errors and healthy hosts dropping to zero indicate that health checks are timing out before the application can respond. With a default health check timeout of 5 seconds and a 30-second interval, if the /health endpoint occasionally takes longer than 5 seconds (e.g., due to transient load), the ALB marks instances unhealthy after two consecutive failures (unhealthy threshold of 2). Increasing the timeout to 10 seconds gives the endpoint more time to respond, preventing false negatives without changing the check frequency.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Increase the health check interval to 60 seconds.
Why it's wrong here
Increasing the health check interval to 60 seconds actually reduces the frequency of health checks. This means the load balancer would take longer to detect an already-unhealthy instance, so traffic could still be routed to a failing backend during that extended window. Worse, it does nothing to fix the underlying issue where the health check endpoint is responding too slowly under momentary load.
- ✓
Increase the health check timeout to 10 seconds.
Why this is correct
Raising the health check timeout to 10 seconds gives the application's health check endpoint more time to respond before the load balancer declares it unhealthy. For example, if the default timeout is 5 seconds and the endpoint occasionally takes 7 seconds under brief CPU or database contention, a 10-second timeout avoids false positives. This directly addresses the cause of the health check failures while still allowing unhealthy instances to be removed if they truly stop responding.
- ✗
Add more EC2 instances to the target group.
Why it's wrong here
Adding more EC2 instances to the target group only spreads incoming traffic across more capacity; it does not change how the health check endpoint behaves on any individual instance. If the health check endpoint is slow or timing out due to an application dependency, memory pressure, or a configuration issue, those new instances will suffer the same failures. Moreover, scaling out increases the number of targets the load balancer must monitor, which does not resolve the root cause of the health check failures.
- ✗
Decrease the healthy threshold to 1.
Why it's wrong here
Decreasing the healthy threshold to 1 means an instance is marked healthy after a single successful health check response. This does not affect the timeout or the reason an instance was marked unhealthy in the first place, so it fails to solve the problem. It can also cause flapping, where an instance alternates between healthy and unhealthy based on one random response, making the target group less stable and potentially increasing dropped requests.
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Same concept, more angles
1 more way 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. A company is running a stateful web application on EC2 instances behind an Application Load Balancer (ALB). Users report intermittent errors. The SysOps admin notices that the ALB's healthy host count is fluctuating. The admin wants to improve the health check configuration to reduce false positives. Which configuration change is most likely to help?
medium- A.Increase the unhealthy threshold count
- B.Reduce the health check interval
- ✓ C.Increase the health check interval
- D.Lower the healthy threshold count
Why C: Increasing the health check interval reduces the frequency of health checks, which helps prevent transient issues (e.g., brief CPU spikes or network jitter) from causing false positives. With a longer interval, the ALB waits longer between checks, giving the instance more time to recover before being marked unhealthy. This stabilizes the healthy host count and reduces unnecessary instance replacement.
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.