Drupal 8: Custom service that gets and sets admin variables

CustomAdminSettingService.php

<?php

namespace Drupal\my_module\Service;

use Drupal\Core\Database\Driver\mysql\Connection;


/**
 * Service that peforms administration work for My Module
 * 
 * This feature allows you to have settings outside of standard Drupal config
 */
class CustomAdminSettingService {

  /**
   * database service
   *
   * @var \Drupal\Core\Database\Driver\mysql\Connection
   */
  protected $databaseService;

  /**
   * Constructs Admin object.
   *
   * @param \Drupal\Core\Database\Driver\mysql\Connection
   */
  public function __construct(Connection $databaseService) {
    $this->databaseService = $databaseService;
  }

  /**
   * Returns a setting from database
   *
   * @return string $setting
   */
  public function getAdminSettingDB($name){
    $setting = $this->databaseService->select('my_module_settings_table', 'm')
      ->fields('m', ['data'])
      ->condition('m.name', $name)
      ->execute()->fetchField();
    $setting = unserialize($setting);
    return $setting;
  }

  /**
   * Inserts or updates a variables in My Module settings table
   *
   * @return string $auth_header
   */
  public function setAdminSettingDB($name, $value){
    // get setting
    $setting = $this->getAdminSettingDB($name);
    //   set setting
    if (!empty($setting)){ // update if it is set
      $query = $this->databaseService->update('my_module_settings_table')
      ->fields([
        'data' => serialize($value),
      ])
      ->condition('name', $name)
      ->execute();
    }
    else { // insert if it is NOT set
      $query = $this->databaseService->insert('my_module_settings_table')
      ->fields([
        'data' => serialize($value),
        'name' => $name,
      ])
      ->execute();
    }
  }
}

my_module.install.php

<?php

/**
 * @file
 * Installation routins for My Module
 */

/**
* Implements hook_schema().
*
* Defines the database-only table used by My Module
*
* @see hook_schema()
*
* @ingroup ti_sync
*/
function my_module_schema() {
  $schema['my_module_settings_table'] = [
    'description' => 'Database-only settings for My Module.',
    'fields' => [
      'id' => [
        'type' => 'serial',
        'not null' => TRUE,
        'description' => 'Primary Key: Unique ID of the setting.',
      ],
      'name' => [
        'type' => 'varchar',
        'length' => 255,
        'not null' => TRUE,
        'description' => 'Name of the setting.',
      ],
      'data' => [
        'type' => 'text',
        'description' => 'Data of the setting.',
      ],
    ],
    'primary key' => ['id'],
    'indexes' => [
      'name' => ['name'],
  ],
  ];
  return $schema;
}