Scheduled scaling in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

Understanding Scheduled Scaling Behavior

You configure an AWS Auto Scaling group with a scheduled scaling action to increase the desired capacity from 2 to 5 instances at 8:00 AM daily. What happens if the current desired capacity is already 6 instances at 8:00 AM?

A The desired capacity is reduced to 5 instances at 8:00 AM as per the scheduled action.

B The desired capacity remains at 6 instances; the scheduled action does not reduce capacity.

C The scheduled action fails and triggers an error notification.

D The Auto Scaling group terminates one instance immediately to match the scheduled capacity.

💡 Hint

Scheduled scaling actions set the desired capacity to the specified value and can scale in or out.

Scheduled scaling actions set the desired capacity of the Auto Scaling group to the specified value. Amazon EC2 Auto Scaling changes the capacity accordingly, including scaling in if the new value is lower than the current desired capacity.

❓ Configuration

intermediate

Correct Scheduled Scaling Configuration

Which of the following AWS CLI commands correctly creates a scheduled scaling action to increase the desired capacity of an Auto Scaling group named webserver-group to 10 instances at 6:00 PM UTC daily?

A aws autoscaling put-scheduled-update-group-action --auto-scaling-group-name webserver-group --scheduled-action-name scale-up-evening --start-time 18:00 --desired-capacity 10

B aws autoscaling put-scheduled-update-group-action --auto-scaling-group-name webserver-group --scheduled-action-name scale-up-evening --start-time 2024-06-01T18:00:00Z --desired-capacity 10 --recurrence '0 18 * * *'

C aws autoscaling put-scheduled-update-group-action --auto-scaling-group-name webserver-group --scheduled-action-name scale-up-evening --start-time 2024-06-01T18:00:00Z --desired-capacity 10

D aws autoscaling put-scheduled-update-group-action --auto-scaling-group-name webserver-group --scheduled-action-name scale-up-evening --recurrence '0 18 * * *' --desired-capacity 10

💡 Hint

Scheduled scaling requires either a start time or a recurrence expression for repeated actions.

Option D correctly uses the --recurrence parameter with a cron expression to schedule the scaling action daily at 18:00 UTC and sets the desired capacity to 10. It omits --start-time because recurrence alone is sufficient.

❓ Architecture

advanced

Designing Scheduled Scaling for Cost Optimization

You manage an application with predictable traffic spikes from 9 AM to 5 PM on weekdays. You want to optimize costs by scaling out before 9 AM and scaling in after 5 PM. Which architecture best supports this using AWS scheduled scaling?

A Configure scheduled scaling to increase capacity at 9 AM and decrease capacity at 5 PM every day including weekends.

B Use a single scheduled scaling action to set desired capacity to high at 9 AM and rely on manual scaling to reduce capacity after 5 PM.

C Create two scheduled scaling actions: one to increase desired capacity at 8:45 AM and another to decrease desired capacity at 5:15 PM on weekdays.

D Use dynamic scaling policies triggered by CPU utilization thresholds instead of scheduled scaling.

💡 Hint

Think about timing and days when traffic spikes occur.

Option C schedules scaling actions just before and after the traffic spike window on weekdays only, ensuring capacity matches demand and reduces costs outside business hours.

❓ security

advanced

Security Best Practices for Scheduled Scaling

Which IAM policy statement least restricts permissions while allowing a user to create and manage scheduled scaling actions for a specific Auto Scaling group named app-group?

A {"Effect": "Allow", "Action": ["autoscaling:PutScheduledUpdateGroupAction", "autoscaling:DeleteScheduledAction"], "Resource": "arn:aws:autoscaling:*:*:autoScalingGroup:*:autoScalingGroupName/app-group"}

B {"Effect": "Allow", "Action": "autoscaling:*", "Resource": "*"}

C {"Effect": "Allow", "Action": ["autoscaling:PutScheduledUpdateGroupAction"], "Resource": "*"}

D {"Effect": "Allow", "Action": ["autoscaling:PutScheduledUpdateGroupAction", "autoscaling:DeleteScheduledAction"], "Resource": "*"}

💡 Hint

Consider least privilege principle and resource scoping.

Option A restricts permissions to only the necessary actions and limits them to the specific Auto Scaling group resource, following best security practices.

✅ Best Practice

expert

Troubleshooting Scheduled Scaling Not Triggering

You set a scheduled scaling action to increase desired capacity at 7:00 AM daily, but the Auto Scaling group does not scale up as expected. Which is the most likely cause?

A The Auto Scaling group has a minimum size higher than the scheduled desired capacity, preventing scaling.

B The scheduled action's start time is in the past and no recurrence is set, so it only ran once and will not run again.

C The scheduled action is missing the desired capacity parameter, so it does nothing.

D The Auto Scaling group is in a suspended state and ignores all scaling actions.

💡 Hint

Check if the scheduled action is configured to repeat or only run once.

If a scheduled scaling action has a start time in the past and no recurrence, it runs only once at that time and does not trigger again. To run daily, a recurrence expression is needed.