The answer is a non-200 status code from the application’s health check URL. Elastic Beanstalk relies on the load balancer to send requests to a configurable path—defaulting to “/”—and any response other than 200 OK causes the instance to be marked unhealthy, even when application logs show no errors. This scenario tests your understanding of how Elastic Beanstalk integrates with the load balancer’s health check system, a common trap on the AWS Certified Developer Associate DVA-C02 exam where candidates overlook that a missing or misconfigured health check endpoint can silently fail without generating log entries. The key insight is that the health check is an external, protocol-level verification, not an application-level error log. Memory tip: “200 or bust”—if your health check doesn’t return a 200, your instance is toast.
DVA-C02 Troubleshooting and Optimization Practice Question
This DVA-C02 practice question tests your understanding of troubleshooting and optimization. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A developer is troubleshooting an AWS Elastic Beanstalk environment that is failing health checks. The environment runs a web application on Tomcat. The developer checks the logs and finds no errors. What is the most likely cause of the health check failure?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The application's health check URL is returning a non-200 status code.
The most likely cause is that the application's health check URL is returning a non-200 status code. Elastic Beanstalk uses the load balancer to perform health checks against a configurable path (default: /). If the application responds with any status other than 200 OK, the load balancer marks the instance as unhealthy, even if the application logs show no errors. This is a common misconfiguration where the health check endpoint is not implemented or returns an unexpected status.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The application's health check URL is returning a non-200 status code.
Why this is correct
The default health check is a 200 response on the root path.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The security group for the instances does not allow traffic from the load balancer.
Why it's wrong here
Elastic Beanstalk configures security groups correctly by default.
✗
The application is throwing exceptions that are not logged.
Why it's wrong here
Exceptions would be logged.
✗
The application is listening on a port other than 80.
Why it's wrong here
Elastic Beanstalk configures the proxy to forward traffic to the correct port.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume health check failures are always due to network or infrastructure issues (security groups, ports) rather than application-level misconfigurations like a missing or incorrect health check endpoint.
Detailed technical explanation
How to think about this question
Elastic Beanstalk health checks are performed by the load balancer (ALB or CLB) sending HTTP GET requests to the configured health check path. The default path for Tomcat environments is '/', but if the application does not serve content at that path (e.g., it expects '/health'), the load balancer receives a 404 or 403, causing health check failure. Under the hood, the load balancer uses HTTP/1.1 and expects a 200 OK response within the configured timeout (default 5 seconds); any other status code or timeout triggers an unhealthy state.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Troubleshooting and Optimization — This question tests Troubleshooting and Optimization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The application's health check URL is returning a non-200 status code. — The most likely cause is that the application's health check URL is returning a non-200 status code. Elastic Beanstalk uses the load balancer to perform health checks against a configurable path (default: /). If the application responds with any status other than 200 OK, the load balancer marks the instance as unhealthy, even if the application logs show no errors. This is a common misconfiguration where the health check endpoint is not implemented or returns an unexpected status.
What should I do if I get this DVA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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