SAP-C02 Continuous Improvement for Existing Solutions Practice Question
A company runs a production application on Amazon ECS with Fargate launch type. The application uses an Application Load Balancer (ALB) to distribute traffic to tasks. The company has configured an Auto Scaling target tracking policy based on average CPU utilization. During a marketing campaign, traffic spikes cause the ALB to return 503 errors. The ECS service dashboard shows that the number of tasks scaled out to the maximum allowed but the CPU utilization remained high. What is the MOST likely cause of the 503 errors?
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 ECS service scaled out to the maximum number of tasks, but the new tasks are not yet registered as healthy with the ALB, or the existing tasks are overwhelmed.
When ECS tasks scale out to the maximum allowed, the ALB may still return 503 errors if the new tasks are not yet registered as healthy (health check grace period or delayed registration) or if the existing tasks are already overwhelmed. The scaling policy reached its maximum, but the tasks cannot handle the traffic, leaving the ALB with no healthy targets to serve requests. Option B is incorrect because target tracking scaling policies typically respond within minutes, but the issue here is that the maximum number of tasks was reached and CPU remained high, not that scaling was too slow. Option C is incorrect because ENI limits for Fargate tasks are per-task and unlikely to cause ALB 503 errors. Option D is incorrect because ALB connection limits are very high and rarely the bottleneck; the error stems from lack of healthy targets.
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 ECS service scaled out to the maximum number of tasks, but the new tasks are not yet registered as healthy with the ALB, or the existing tasks are overwhelmed.
Why this is correct
When max tasks is reached and CPU is high, tasks may be overwhelmed; also, if health check grace period is too short, new tasks may be considered unhealthy and dropped.
- ✗
The target tracking scaling policy takes too long to trigger, and the service cannot scale quickly enough.
Why it's wrong here
Target tracking triggers when CPU exceeds target, but the service may have reached max tasks; the policy itself is responsive.
- ✗
The Fargate tasks have exhausted their elastic network interface (ENI) limits.
Why it's wrong here
Fargate tasks have ENI limits per task but the error is at the ALB level, not network interface exhaustion.
- ✗
The ALB connection limit has been exceeded due to the traffic spike.
Why it's wrong here
ALB can handle millions of connections; the error is more likely due to lack of healthy targets.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAP-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 SAP-C02 exam.