200 return code on ‘POST /wp-admin/admin-ajax.php’ while NOT logged in

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wp-admin/admin-ajax.php is the script used by any plugin or theme using WP Ajax API and Ajax actions can be registered for non-logged in users. For example:

//For logged in users
add_action( 'wp_ajax_my_action', 'my_action_callback' );
//For non-logged in users
add_action( 'wp_ajax_nopriv_my_action', 'my_action_callback' );

There is no problem on that. See WP Ajax documentation for more information.