public function purge($lifetime = LibSessionsDomainEntitySession::MAX_LIFETIME, $guestOnly = true)
    {
        $past = time() - $lifetime;

        $query = $this->getQuery()->delete()->where('time < '.$past);

        if ($guestOnly) {
            $query->where('guest', '=', 1);
        }

        return (boolean) $this->getStore()->execute($query);
    }