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Difficulty: HardIdentifying and Cleaning Up Underutilized Resources

A SysOps administrator needs to identify and safely decommission underutilized Application Load Balancers (ALBs) to optimize costs across a production AWS account. The administrator accesses the AWS Trusted Advisor Cost Optimization dashboard and notes several ALBs flagged as idle.

Which of the following describes the most accurate method to verify these load balancers are idle and the safest sequence to delete them?

  1. A
    Configure a CloudWatch Logs metric filter on the ALB access logs to track active requests. Set the CloudWatch Log Group retention period to 7 days, and delete any ALB that has not written to its log stream within that timeframe to automatically stop log storage costs.
  2. B
    Enable Detailed Monitoring on the identified ALBs to access 1-minute granularity for the ActiveConnectionCount metric. If the average connections over 7 days are less than 100, delete the ALB immediately and release any associated Elastic IP addresses to avoid idle address fees.
  3. Query the CloudWatch RequestCount metric using the Sum statistic over the last 7 days. If the total requests are less than 100, update any Route 53 alias records pointing to the ALB to redirect traffic to a backup resource, wait for the DNS TTL to expire, and then delete the ALB.Answer
  4. D
    Check the Cost Allocation Tags on the ALBs using AWS Cost Explorer to confirm zero billing activity over the last 7 days. Once verified, delete the ALBs first, and then update Route 53 CNAME records to point to a static S3 website hosting endpoint.

Answer

Query the CloudWatch RequestCount metric using the Sum statistic over the last 7 days. If the total requests are less than 100, update any Route 53 alias records pointing to the ALB to redirect traffic to a backup resource, wait for the DNS TTL to expire, and then delete the ALB.
The correct option outlines the standard AWS Trusted Advisor threshold for identifying idle ALBs, which is having a RequestCount of less than 100 over a 7-day period. By using the Sum statistic, the administrator can confirm the total request volume. The decommissioning workflow is safe because it updates Route 53 records first and waits for the TTL to expire, preventing client connection failures before the resource is deleted.

Step-by-Step Solution

1
Verify ALB idle status via CloudWatch metrics.
Check the RequestCount metric with a Sum statistic over a 7-day period to ensure total requests are under 100.
This matches the criteria used by AWS Trusted Advisor for identifying underutilized Application Load Balancers and guarantees actual network idle status.
2
Perform pre-decommissioning DNS updates.
Update the Route 53 DNS records (such as Alias records pointing to the ALB) to route traffic to a static maintenance page or backup system.
Modifying DNS configuration prior to deletion prevents clients from experiencing connection errors once the load balancer is removed.
3
Wait for DNS TTL expiration and delete the resource.
Allow the TTL duration of the previous DNS record to elapse, then safely delete the ALB in the EC2 Console or via AWS CLI.
Waiting for the TTL to expire ensures all DNS resolvers and client caches have updated their records, preventing any remaining traffic from reaching the deleted ALB.

Key Concept

Safely identifying and decommissioning idle Application Load Balancers (ALBs) involves verifying usage using the RequestCount metric (Sum statistic over 7 days) and updating Route 53 DNS records before deleting the resource to avoid traffic blackholing.
Estimated Time:2m 0s
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Topics

Identifying and Cleaning Up Underutilized Resources

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