EC2 Cost Optimization Lambda

An automated AWS Lambda solution that performs cost-saving cleanups on unused or idle EC2-related resources such as:

• Unattached EBS volumes
• Old EBS snapshots
• Idle EC2 instances
• Unused Elastic IPs
• Unused Load Balancers
• Old AMIs and their snapshots

The Lambda function is triggered daily via Amazon EventBridge (cron), and logs cleanup results to Amazon S3 and sends SNS notifications.

---

Features

• EBS Volume Cleanup: Deletes unattached volumes older than a configurable threshold.
• EBS Snapshot Cleanup: Deletes snapshots not attached to in-use volumes or volumes that no longer exist.
• Idle EC2 Notification: Identifies running instances with low CPU usage for 7 days.
• Elastic IP Release: Releases unassociated Elastic IPs to avoid unnecessary billing.
• Load Balancer Cleanup: Deletes ALBs/NLBs with no registered targets.
• AMI Cleanup: Deregisters old AMIs and deletes their associated snapshots.
• S3 Logging: Uploads structured JSON logs to a designated S3 bucket.
• SNS Alerts: Sends cleanup and idle instance notifications via SNS.

---

EventBridge Schedule (Cron)

EventBridge triggers the Lambda function at a fixed interval (e.g., once daily):

cron(0 2 * * ? *)  # Every day at 2:00 AM UTC

Configure via AWS Console.

---

IAM Permissions Required

Attach this inline policy to the IAM Role assigned to the Lambda:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "ec2:DescribeImages", "ec2:DescribeInstances", "ec2:DescribeVolumes",
        "ec2:DescribeSnapshots", "ec2:DeleteSnapshot", "ec2:DeleteVolume",
        "ec2:ReleaseAddress", "ec2:DeregisterImage", "ec2:DescribeAddresses",
        "elasticloadbalancing:DescribeLoadBalancers",
        "elasticloadbalancing:DescribeTargetGroups",
        "elasticloadbalancing:DescribeTargetHealth",
        "elasticloadbalancing:DeleteLoadBalancer",
        "cloudwatch:GetMetricStatistics",
        "sns:Publish"
      ],
      "Resource": "*"
    }
  ]
}

---

Environment Variables

Variable Name	Description	Default Value
EBS_VOLUME_AGE_DAYS	Max age of unattached volumes to keep (in days)	7
SNAPSHOT_RETENTION_DAYS	Max age of snapshots to retain (in days)	30
AMI_RETENTION_DAYS	Max age of AMIs to keep (in days)	60
IDLE_CPU_THRESHOLD	CPU % threshold to detect idle EC2 instances	5.0
LB_MIN_AGE_MINUTES	Minimum age for load balancers to be considered (in min)	60
LOG_S3_BUCKET	Target S3 bucket for uploading logs	ec2-cost-logs
SNS_TOPIC_ARN	SNS topic ARN for notifications	(required)

---

Deployment

1. Package Lambda with all Python files
2. Zip and Upload via AWS Console.
3. Attach IAM Role with the inline policy shown above.
4. Create EventBridge Rule with desired cron expression.
5. Set environment variables in the Lambda configuration.

---

Log Structure (S3 JSON)

Each JSON log entry uploaded to S3 looks like:

{
  "resource_id": "vol-123456",
  "action": "deleted",
  "resource_type": "EBS Volume",
  "reason": "Unattached and older than 7 days",
  "timestamp": "2025-06-01T10:05:23Z"
}

---

SNS Notifications

Topic 1: Cleanup Summary

• Subject: EC2 Cost Optimization Cleanup Summary
• Details: Lists number of deleted volumes, snapshots, AMIs, etc.

Topic 2: Idle Instance Alerts

• Subject: EC2 Idle Resource Notification
• Details: Lists EC2 instances with consistently low CPU usage.

---