protected function getTtlAndKey(array &$args)/*# : array */
    {
        if (is_numeric($args[0])) {
            $ttl = (int) array_shift($args);
            $key = $this->generateKey($args);
        } else {
            $key = $this->generateKey($args);
            $ttl = $this->ttl;
        }
        return [$ttl, $key];
    }