Source

File: wp-includes/post.php

function _count_posts_cache_key( $type = 'post', $perm = '' ) {
	$cache_key = 'posts-' . $type;

	if ( 'readable' === $perm && is_user_logged_in() ) {
		$post_type_object = get_post_type_object( $type );

		if ( $post_type_object && ! current_user_can( $post_type_object->cap->read_private_posts ) ) {
			$cache_key .= '_' . $perm . '_' . get_current_user_id();
		}
	}

	return $cache_key;
}