DVA-C02 Troubleshooting and Optimization Practice Question
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?
⚠ Common exam trap
A common mix-up: 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.
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
✓
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.
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
Elastic Beanstalk environments rely on health checks, typically performed by the associated Load Balancer, to determine the operational status of application instances. If the configured health check URL, often the root path "/", consistently returns a non-200 HTTP status code, the Load Balancer will mark the instance as unhealthy. This leads to the instance being removed from the target group, preventing traffic, and can cause Elastic Beanstalk to report a "Degraded" or "Severe" environment health status, triggering instance replacement or environment instability.
- ✗
The security group for the instances does not allow traffic from the load balancer.
Why it's wrong here
Elastic Beanstalk automatically provisions and configures the necessary AWS resources, including security groups, to ensure proper communication within the environment. By default, it creates security group rules that explicitly permit inbound traffic from the associated Load Balancer to the EC2 instances on the required application port. Therefore, a misconfigured security group blocking load balancer traffic is highly improbable unless manually altered post-deployment, making it an unlikely cause for general application issues.
- ✗
The application is throwing exceptions that are not logged.
Why it's wrong here
Modern application frameworks and standard server configurations within Elastic Beanstalk environments are designed to capture and log application exceptions. These logs are typically written to standard output, application-specific log files on the EC2 instances, or forwarded to CloudWatch Logs. While exceptions indicate application errors, the absence of logging them is highly improbable; instead, the logs themselves would contain the evidence of the exceptions, which would then be analyzed during troubleshooting.
- ✗
The application is listening on a port other than 80.
Why it's wrong here
Elastic Beanstalk environments typically employ a reverse proxy, such as Nginx or Apache, running on port 80 (or 443 for HTTPS) on the EC2 instances. This proxy is automatically configured by Elastic Beanstalk to forward incoming requests to the application process, which can be listening on any internal port (e.g., 5000, 8080). As long as the proxy is correctly configured to point to the application's actual listening port, the external port 80 remains the entry point, making the internal port irrelevant to external connectivity issues.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DVA-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 DVA-C02 exam.