Alarm actions (SNS, Auto Scaling) in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

What happens when a CloudWatch alarm triggers an SNS notification?

You have a CloudWatch alarm configured to send a notification to an SNS topic when CPU usage exceeds 80%. What is the expected behavior when the alarm state changes to ALARM?

A The SNS topic sends the notification message to all its subscribed endpoints immediately.

B The SNS topic queues the message but does not send it until manually triggered.

C The CloudWatch alarm automatically scales the EC2 instances without sending any notification.

D The alarm state change is logged but no notification is sent unless a Lambda function is attached.

💡 Hint

Think about how SNS works with subscriptions and notifications.

When a CloudWatch alarm triggers, it sends a message to the SNS topic, which immediately pushes the notification to all subscribed endpoints such as email, SMS, or Lambda.

❓ Architecture

intermediate

How does an Auto Scaling group respond to a CloudWatch alarm action?

An Auto Scaling group is configured with a CloudWatch alarm that triggers a scale-out policy when average CPU usage exceeds 70%. What is the expected result when the alarm triggers?

A The Auto Scaling group waits for manual approval before scaling out.

B The Auto Scaling group sends an SNS notification but does not change the number of instances.

C The Auto Scaling group launches additional instances according to the scaling policy immediately.

D The Auto Scaling group terminates instances to reduce CPU usage.

💡 Hint

Consider what a scale-out policy means for an Auto Scaling group.

When the alarm triggers a scale-out policy, the Auto Scaling group automatically launches more instances to handle increased load.

❓ security

advanced

Which IAM permission is required for CloudWatch to trigger Auto Scaling actions?

To allow CloudWatch alarms to trigger Auto Scaling policies, which IAM permission must be granted to the CloudWatch service or role?

A "cloudwatch:PutMetricAlarm" permission on the alarm resource.

B "ec2:TerminateInstances" permission on the EC2 instances.

C "sns:Publish" permission on the SNS topic resource.

D "autoscaling:ExecutePolicy" permission on the Auto Scaling group resource.

💡 Hint

Think about what action CloudWatch needs to perform to scale instances.

CloudWatch needs the "autoscaling:ExecutePolicy" permission to invoke scaling policies on the Auto Scaling group.

✅ Best Practice

advanced

What is a best practice when configuring SNS topics for CloudWatch alarm notifications?

When setting up SNS topics to receive CloudWatch alarm notifications, which practice improves security and reliability?

A Send notifications only to email endpoints without using encryption or access control.

B Use least privilege by restricting SNS topic access to only necessary subscribers and encrypt messages with AWS KMS.

C Allow open public access to the SNS topic so anyone can subscribe and receive notifications.

D Disable delivery retries to avoid duplicate notifications.

💡 Hint

Consider how to protect sensitive alarm notifications and control access.

Restricting access and encrypting messages ensures only authorized subscribers receive notifications securely.

🧠 Conceptual

expert

What is the sequence of events when a CloudWatch alarm triggers an Auto Scaling scale-in action and sends an SNS notification?

Order the following steps correctly when a CloudWatch alarm triggers a scale-in policy and sends a notification via SNS.

A 1,4,2,3

B 1,2,4,3

C 4,1,2,3

D 1,4,3,2

💡 Hint

Think about what happens first and how CloudWatch triggers multiple actions.

First, the alarm state changes. Then CloudWatch triggers both the scale-in policy and SNS notification. The SNS notification is sent while the Auto Scaling group terminates instances.