ECS service auto scaling in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

ECS Service Auto Scaling Behavior

What happens when an ECS service's auto scaling policy triggers a scale-out action?

A The ECS service scales the underlying EC2 instances but does not change the number of tasks.

B The ECS service stops existing tasks before launching new ones to maintain the current count.

C The ECS service queues scaling requests and applies them only during the next deployment.

D The ECS service immediately launches new tasks to match the desired count set by the scaling policy.

💡 Hint

Think about how ECS manages task counts when scaling.

When an ECS service auto scaling policy triggers a scale-out, ECS immediately launches new tasks to reach the new desired count.

❓ Configuration

intermediate

Configuring ECS Service Auto Scaling Target

Which AWS resource must you specify as the scalable target when configuring ECS service auto scaling?

A The ECS task definition revision number as a scalable target with resource ID format: taskdef/task-def-name

B The ECS service's task count as a scalable target with resource ID format: service/cluster-name/service-name

C The ECS cluster's EC2 instance count as a scalable target with resource ID format: cluster/cluster-name

D The ECS service's load balancer target group as a scalable target with resource ID format: targetgroup/target-group-name

💡 Hint

Auto scaling targets the number of tasks running in the service.

The scalable target for ECS service auto scaling is the ECS service's task count, identified by the resource ID format service/cluster-name/service-name.

❓ Architecture

advanced

Designing ECS Auto Scaling with CloudWatch Alarms

You want to scale your ECS service based on CPU usage. Which architecture component is essential to trigger scaling actions?

A A CloudWatch alarm monitoring the ECS service CPU utilization that triggers a scaling policy.

B An AWS Lambda function that polls ECS tasks and adjusts the desired count manually.

C An S3 event notification that triggers scaling when new objects are uploaded.

D A Route 53 health check that disables scaling when the service is unhealthy.

💡 Hint

Auto scaling reacts to metrics monitored by CloudWatch alarms.

CloudWatch alarms monitor CPU usage and trigger scaling policies to adjust ECS service task counts automatically.

❓ security

advanced

IAM Permissions for ECS Auto Scaling

Which IAM permission is required for an ECS service auto scaling role to update the desired task count?

A "cloudwatch:PutMetricAlarm" permission on CloudWatch alarms.

B "autoscaling:CreateScalingPolicy" permission on the Auto Scaling group.

C "ecs:UpdateService" permission on the ECS service resource.

D "ec2:RunInstances" permission on the EC2 instances.

💡 Hint

Think about what action changes the number of running tasks.

The ECS service auto scaling role needs "ecs:UpdateService" permission to change the desired count of tasks in the service.

✅ Best Practice

expert

Best Practice for ECS Service Auto Scaling Cooldown Period

What is the best practice for setting the cooldown period in ECS service auto scaling policies?

A Set the cooldown period to allow enough time for tasks to start and stabilize before another scaling action.

B Set the cooldown period to zero to allow immediate consecutive scaling actions for fast response.

C Set the cooldown period longer than the deployment time of the ECS service to avoid any scaling.

D Set the cooldown period to match the CloudWatch alarm evaluation period regardless of task startup time.

💡 Hint

Consider how quickly tasks become healthy after scaling.

The cooldown period should be long enough to let new tasks start and stabilize, preventing rapid scaling fluctuations.