SOA-C02 Monitoring, Logging, and Remediation Practice Question
A company has an application running on Amazon EC2 instances behind an Application Load Balancer (ALB). The application logs show intermittent 503 errors. The ALB access logs show that the errors occur when the target response time exceeds 30 seconds. Which configuration change should the SysOps administrator make to reduce the number of 503 errors without affecting the application's behavior?
⚠ Common exam trap
Test-takers frequently confuse the ALB idle timeout with the target group deregistration delay or health check settings, mistakenly thinking that adjusting health checks or deregistration will fix timeout-related 503 errors, when the root cause is the ALB's connection timeout parameter.
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 idle timeout setting on the ALB
The 503 errors occur when the target response time exceeds 30 seconds, which matches the default idle timeout of the Application Load Balancer. By increasing the idle timeout setting on the ALB to a value higher than the application's maximum expected response time (e.g., 60 or 120 seconds), the ALB will wait longer before closing the connection, preventing premature 503 errors while the backend is still processing the request.
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 deregistration delay on the target group
Why it's wrong here
Deregistration delay controls how long the ALB keeps a target in service while it is being deregistered, allowing in-flight requests to complete. It does not govern the time the load balancer waits for a response to a new request; it applies only during connection draining. Therefore, increasing this delay will not resolve timeouts caused by requests taking longer than the ALB's idle timeout.
- ✓
Increase the idle timeout setting on the ALB
Why this is correct
The ALB idle timeout is the maximum time the load balancer waits for a response from the target after forwarding a request. If the application takes longer than this timeout to send a response, the ALB closes the connection and the client receives an error. Increasing the idle timeout gives long-running requests more time to complete, so this is the correct fix.
- ✗
Enable cross-zone load balancing on the ALB
Why it's wrong here
Cross-zone load balancing allows the ALB to distribute traffic evenly across all registered targets in every Availability Zone, rather than only in the zone where each load balancer node is located. It improves utilization and fault tolerance, but it has no effect on the load balancer's request timeout settings or the time a target has to respond. Thus, enabling it would not address timeouts due to slow application responses.
- ✗
Decrease the health check interval on the target group
Why it's wrong here
Decreasing the health check interval causes the ALB to send health checks more frequently, which may speed up detection of failed targets. However, it does not change the connection timeout for client requests, and more frequent checks can increase the chance of a target being marked unhealthy if a response is momentarily delayed. This adjustment is unrelated to the allowed duration for application responses.
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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. An application running on Amazon EC2 instances behind an Application Load Balancer (ALB) is experiencing intermittent 5xx errors. CloudWatch metrics show that the ALB's 'HTTPCode_ELB_5XX_Count' is elevated. What is the MOST likely cause?
medium- A.The target instances are returning HTTP 503 errors.
- B.The target instances have high latency but are still responding.
- ✓ C.The load balancer is timing out waiting for a response from the target.
- D.Client requests are malformed and being rejected by the load balancer.
Why C: When the ALB's 'HTTPCode_ELB_5XX_Count' is elevated, it indicates that the load balancer itself is generating the 5xx error, not the target. The most common cause is that the load balancer is timing out while waiting for a response from the target instances, which occurs when the target takes longer than the configured idle timeout (default 60 seconds) to respond. This results in the ALB returning a 504 Gateway Timeout error, which is counted in the ELB 5xx metric.
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.