hardMultiple ChoiceObjective-mapped
CV0-004 Practice Question: A company has a hybrid cloud environment with…
A company has a hybrid cloud environment with on-premises servers and AWS. They deploy a new application using AWS Elastic Beanstalk with a load balancer and auto scaling group. The application is a Node.js API that connects to an RDS MySQL database. After deployment, users report that the API returns a '500 Internal Server Error' intermittently. The application logs show 'ETIMEDOUT' errors when connecting to the database. The database is deployed in a private subnet with a security group that allows inbound traffic from the Elastic Beanstalk environment's security group. The database connection string uses the RDS endpoint. The same application works perfectly when deployed on-premises. What is the most likely cause?
⚠ Common exam trap
Watch out — candidates often assume security group misconfiguration is the cause, but 'ETIMEDOUT' specifically indicates a network layer reachability problem (routing or VPC isolation) rather than a firewall or authentication issue.
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 Elastic Beanstalk environment is in a different VPC or subnet that cannot reach the RDS instance
The intermittent 'ETIMEDOUT' errors indicate a network connectivity issue between the Elastic Beanstalk environment and the RDS database. Since the application works on-premises, the problem is specific to the AWS networking configuration. The most likely cause is that the Elastic Beanstalk environment is deployed in a different VPC or subnet that lacks routing or a VPC peering connection to reach the RDS instance's private subnet, causing timeouts when the load balancer or auto scaling group instances attempt to connect.
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 database connection string uses the wrong port number
Why it's wrong here
The default MySQL port is 3306, which is standard and unlikely to be wrong.
- ✓
The Elastic Beanstalk environment is in a different VPC or subnet that cannot reach the RDS instance
Why this is correct
Network connectivity between VPCs or subnets is likely misconfigured, causing timeouts.
- ✗
The security group attached to the RDS instance does not allow traffic from the Elastic Beanstalk environment
Why it's wrong here
The security group is already configured to allow inbound from the Elastic Beanstalk security group.
- ✗
The RDS instance is in a failed state and needs to be rebooted
Why it's wrong here
The database is running; ETIMEDOUT indicates network issue, not database failure.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This CV0-004 practice question is part of Courseiva's free CompTIA 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 CV0-004 exam.