lambda_fucntion.py

import boto3
from botocore.exceptions import ClientError

def lambda_handler(event, context):
    ec2 = boto3.client('ec2')

    # Get running instances
    instance_response = ec2.describe_instances(
        Filters=[{'Name': 'instance-state-name', 'Values': ['running']}]
    )

    active_instance_ids = set()
    for reservation in instance_response['Reservations']:
        for instance in reservation['Instances']:
            active_instance_ids.add(instance['InstanceId'])

    # Get all snapshots owned by account
    snapshots_response = ec2.describe_snapshots(OwnerIds=['self'])

    for snapshot in snapshots_response['Snapshots']:
        snapshot_id = snapshot['SnapshotId']
        volume_id = snapshot.get('VolumeId')

        # Snapshot not linked to any volume
        if not volume_id:
            ec2.delete_snapshot(SnapshotId=snapshot_id)
            print(f"Deleted snapshot {snapshot_id} (no volume attached)")
            continue

        try:
            volume_response = ec2.describe_volumes(VolumeIds=[volume_id])
            volume = volume_response['Volumes'][0]

            # Volume exists but not attached to any instance
            if not volume['Attachments']:
                ec2.delete_snapshot(SnapshotId=snapshot_id)
                print(f"Deleted snapshot {snapshot_id} (volume unused)")

            else:
                # Volume attached → check instance state
                for attach in volume['Attachments']:
                    if attach['InstanceId'] not in active_instance_ids:
                        ec2.delete_snapshot(SnapshotId=snapshot_id)
                        print(f"Deleted snapshot {snapshot_id} (instance stopped/terminated)")

        except ClientError as e:
            if e.response['Error']['Code'] == 'InvalidVolume.NotFound':
                ec2.delete_snapshot(SnapshotId=snapshot_id)
                print(f"Deleted snapshot {snapshot_id} (volume not found)")