Large WordPress CRON job

I’m programming the integration with external API (real estate). I have one CRON job which is planned for at 1 o’clock am. It’s running very well because I’m using server CRON initialize instead WP CRON standard so It’s running at the right time.

wp_delete_auto_drafts() deletes links in menus

Since yesterday the wp_scheduled_auto_draft_delete cron job somehow deletes all page entries from our menus. All entries in the table wp_postmeta with meta_key = '_menu_item_object' and meta_value = 'page' get deleted in the process. By tracing back the DELETE query I found out that the menu entries are deleted by a function called _wp_delete_post_menu_item. I got the following stacktrace for that function:

Do WordPress cron jobs slow down page loading?

If a user visits a site and his visit triggers a cron job that is quite intensive, the page load speed will be slower for him right? As I understand the page doesn’t wait for the cron job to execute before loading, but since the cron job would be running in parallel, it might still be the case that the page loads slower since the server is busy right?