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ECS Services

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ECS services are responsible for running and maintaining a specified number of task instances to ensure that your application is always available and can either scale up or down based on demand. An ECS service defines the desired state of a task and is created within a specified ECS cluster. Servic…

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AWS Certified Solutions Architect - ECS Services Example Questions

Test your knowledge of ECS Services

Question 1

Your team is deploying an Amazon ECS service on the EC2 launch type using the bridge network mode. You plan to run multiple tasks of the same service on each EC2 instance and place the service behind an Application Load Balancer. How should you configure port mappings so the ALB can route traffic to all tasks on the same host without port conflicts?

Correct Answer: Use dynamic port mapping

In ECS on EC2 using the bridge network mode with multiple tasks of the same service per host, static host ports would collide. Dynamic port mapping (setting hostPort to 0 while exposing a fixed containerPort) lets ECS allocate an ephemeral host port for each task and automatically registers that host:port with the ALB target group (instance target type). This enables the ALB to route traffic to every task on the instance without port conflicts. Static port mapping only works cleanly if you run a single task per host. Excluding port mappings prevents the ALB from reaching the containers. "Create an EC2 instance mapping" is not an ECS configuration concept.

Question 2

You need an Amazon ECS service to automatically adjust the number of running tasks to maintain a specified average CPU utilization (for example, 60%). Which ECS service scaling policy should you configure?

Correct Answer: Target tracking scaling

Target tracking scaling is designed to keep a metric, such as ECSServiceAverageCPUUtilization, at a specified target value by automatically increasing or decreasing the number of running tasks in your ECS service. It behaves like a thermostat: you set a target (for example, 60% CPU) and Application Auto Scaling adjusts task count to maintain it. Step scaling, while capable of reacting to CPU via CloudWatch alarms, requires manual threshold tuning and does not inherently aim to maintain a target level. Scheduled scaling is time-based and not driven by CPU utilization. Simple scaling is a legacy policy type for Auto Scaling groups and is not the appropriate choice for ECS service scaling.

Question 3

Your application has been deployed on Amazon ECS, and you want to continuously monitor its performance. Which AWS service should you use to collect logs and metrics from your ECS containers?

Correct Answer: Amazon CloudWatch

Amazon CloudWatch enables you to monitor and analyze logs and metrics from your Amazon ECS containers. CloudWatch provides powerful analytical features, enabling you to visualize performance data, set alarms, and troubleshoot issues.

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