protected function getNewRatio($key, $limit, $milliseconds)
    {
        $lastRequest = $this->getLastRequest($key) ?: 0;
        $lastRatio   = $this->getLastRatio($key) ?: 0;

        $diff = (microtime(1) - $lastRequest) * 1000;

        $newRatio = $lastRatio - $diff;
        $newRatio = $newRatio < 0 ? 0 : $newRatio;
        $newRatio+= $milliseconds/$limit;

        return $newRatio;
    }