DOP-C02 Monitoring and Logging Practice Question
A company runs a containerized application on Amazon ECS with Fargate launch type. The application consists of three microservices: frontend, backend, and database. The ECS cluster is in a VPC with public and private subnets. The frontend service is publicly accessible via an Application Load Balancer (ALB) in public subnets. The backend service communicates with the database service, which runs as a stateful service with persistent storage using Amazon EFS. The DevOps team is using CloudWatch Container Insights and has enabled Prometheus metrics for the ECS cluster. Recently, the team observed that the frontend service's response time has increased significantly, and some requests are timing out. The team checked the ALB metrics and saw an increase in 5xx errors. They also noticed that the backend service's CPU utilization is high, and the database service's disk I/O is high. The team suspects a bottleneck in the backend service. Which course of action should the team take FIRST to identify the root cause?
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
✓
Check the backend service's application logs in CloudWatch Logs to identify errors or slow database queries.
The first step is to analyze the backend service's application logs to identify any errors or slow operations. High CPU and disk I/O may be caused by inefficient queries or code issues. Option A is incorrect because disabling health checks would hide the problem and could route traffic to unhealthy tasks. Option B is incorrect because migrating to RDS does not address the immediate issue and is a significant change without root cause analysis. Option D is incorrect because increasing the desired count without understanding the root cause may temporarily alleviate load but does not fix underlying performance issues and can increase costs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Disable the health check for the backend service in the ALB target group.
Why it's wrong here
Disabling the health check for the backend service in the ALB target group is incorrect because health checks are a safety mechanism that removes unhealthy tasks from rotation. Without them, the ALB continues routing traffic to tasks that are failing or resource-constrained, which increases latency and 5xx errors for users. This action hides the symptom rather than diagnosing the underlying performance issue, and it does not provide any insight into why the backend is slow.
- ✗
Migrate the database service to Amazon RDS for better performance.
Why it's wrong here
Migrating the database service to Amazon RDS for better performance is not the appropriate first step because the performance issue may originate from inefficient SQL queries, missing indexes, or a database connection pool exhaustion, none of which are solved by a different database platform. Additionally, migrating is a significant, lengthy, and risky change that should only be considered after a proper diagnosis. Without examining application logs or query metrics first, this action could introduce new issues and is not a targeted remediation.
- ✓
Check the backend service's application logs in CloudWatch Logs to identify errors or slow database queries.
Why this is correct
Checking the backend service's application logs in CloudWatch Logs is the correct initial action because it provides direct visibility into application errors, database query execution times, and slow transactional paths. These logs, combined with ECS task metrics and ALB access logs, help isolate whether the high latency is due to application code, database contention, or an upstream dependency. Logs are the least intrusive and most informative diagnostic step, enabling an evidence-based decision before changing infrastructure.
- ✗
Increase the desired count of the backend service to reduce load per task.
Why it's wrong here
Increasing the desired count of the backend service to reduce load per task is not the right answer because it assumes the bottleneck is CPU or concurrency capacity, but the root cause could be a slow database query, an external API call, or a memory leak. Simply adding tasks increases cost and operational complexity without guaranteeing any improvement, and it may even worsen load on a database if the new tasks generate more queries. The issue must first be diagnosed through logs and metrics to determine whether horizontal scaling would even help.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DOP-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 DOP-C02 exam.