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day-18/README.md

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+# AWS Cloud Cost Optimization - Identifying Stale Resources
+
+## Identifying Stale EBS Snapshots
+
+In this example, we'll create a Lambda function that identifies EBS snapshots that are no longer associated with any active EC2 instance and deletes them to save on storage costs.
+
+### Description:
+
+The Lambda function fetches all EBS snapshots owned by the same account ('self') and also retrieves a list of active EC2 instances (running and stopped). For each snapshot, it checks if the associated volume (if exists) is not associated with any active instance. If it finds a stale snapshot, it deletes it, effectively optimizing storage costs.
+
+
+

day-18/ebs_stale_snapshosts.py

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+import boto3
+
+def lambda_handler(event, context):
+    ec2 = boto3.client('ec2')
+
+    # Get all EBS snapshots
+    response = ec2.describe_snapshots(OwnerIds=['self'])
+
+    # Get all active EC2 instance IDs
+    instances_response = ec2.describe_instances(Filters=[{'Name': 'instance-state-name', 'Values': ['running', 'stopped']}])
+    active_instance_ids = set()
+
+    for reservation in instances_response['Reservations']:
+        for instance in reservation['Instances']:
+            active_instance_ids.add(instance['InstanceId'])
+
+    # Iterate through each snapshot and delete if it's stale
+    for snapshot in response['Snapshots']:
+        snapshot_id = snapshot['SnapshotId']
+        if 'VolumeId' in snapshot and snapshot['VolumeId'] not in active_instance_ids:
+            ec2.delete_snapshot(SnapshotId=snapshot_id)
+            print(f"Deleted stale EBS snapshot {snapshot_id}.")