Is the config object adapted to store datas from many users ( for the purpose of a subscription custom module )?

Question

I have created a custom module that allows to subscribe to some news.

Each user ( and there will be thousands of them ) can register to some news category using that form

On form submit, the couple [loti, emails] is stored in a config object, as such:

 public function addSubscriberFromLot($lot, $userEmail) {
    $config = \Drupal::configFactory()
      ->getEditable('my_module_news_subscription.settings');
    $subscribersforLot = $config->get($lot);
    if ($subscribersforLot === null) {
      $config->set($lot, [$userEmail])->save();
    }
    elseif ($subscribersforLot !== null && !(in_array($userEmail, $subscribersforLot))) {
      array_push($subscribersforLot, $userEmail);
      $config->set($lot, $subscribersforLot)->save();
    }
  }

the config schema being

my_module_news_subscription.settings:
  type: mapping
  mapping:
    lot1:
      type: sequence
      label: ‘lot 1’
      sequence:
        type: string
        label: 'Email of subscribers'
    lot2:
      type: sequence
      label: ‘lot 2’
      sequence:
        type: string
        label: 'Email of subscribers'
    lot3:
      type: sequence
      label: ‘lot 3’
      sequence:
        type: string
        label: 'Email of subscribers'
    lot4:
      type: sequence
      label: ‘lot 4’
      sequence:
        type: string
        label: 'Email of subscribers'
    lot5:
      type: sequence
      label: ‘lot 5’
      sequence:
        type: string
        label: 'Email of subscribers'

Is there anything wrong with using that config object for that purpose ?

Can this withstand thousands of entries ?

Is there a more adapted way of store that datas ?

Answer 1

Configuration defines your site. Users are not configuration, so neither would per-user settings be configuration.

If you need to save data per user, you can use the user.data service.