CodeIgniter 3 is generating a session file on each request, why?

$autoload['libraries'] = array('session');

$config['sess_driver']                  = 'database';
$config['sess_cookie_name']             = 'ci_session';
$config['sess_expiration']              = 21600;
$config['sess_use_database']            = false;
$config['sess_table_name']              = 'ci_sessions';
$config['sess_match_ip']                = false;
$config['sess_time_to_update']          = 300;
$config['sess_save_path']               = APPPATH . "cache/sessions/";

CREATE TABLE `sessions` (
  `id` varchar(40) NOT NULL,
  `ip_address` varchar(45) NOT NULL,
  `timestamp` int(10) UNSIGNED NOT NULL DEFAULT '0',
  `data` blob NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8 ROW_FORMAT=COMPACT;

<?php                                                                                                                                                                                           
defined('BASEPATH') OR exit('No direct script access allowed');

class MY_Session extends CI_Session {

    public function __construct(array $params = array())
    {   
        if ( $this->ignore_sessions() )
            return;
        parent::__construct();
    }   

    function ignore_sessions()
    {   
        $uri = str_replace ("//", "/", $_SERVER['REQUEST_URI']);
        if ( strpos($uri, '/ignore_this_controller/') === 0 ) 
            return true;
        return false;
    }   
}

$autoload['libraries'] = array('session')

<link rel="manifest" href="manifest.json">

<link rel="manifest" href="manifest.json" crossorigin="use-credentials">