DynamoDB - Optimistic Lock using timestamp

optimistic_lock.py

    dynamodb = boto3.resource('dynamodb')
    table = dynamodb.Table(ddb_table)
 
    table.put_item(
        Item={
                'device_id': event['clientId'],
                'timestamp': str(event['timestamp']),
                'status': event['eventType']
            },
        ConditionExpression=':ts >= #ts_old OR attribute_not_exists(#ts_old)',
        ExpressionAttributeValues={':ts': str(event['timestamp']) },
        ExpressionAttributeNames={'#ts_old': 'timestamp'}
    )