public static function fetch($params) {
        $cache = cache::make('core', 'coursecompletion');

        $key = $params['userid'] . '_' . $params['course'];
        if ($hit = $cache->get($key)) {
            return $hit['value'];
        }

        $tocache = self::fetch_helper('course_completions', __CLASS__, $params);
        $cache->set($key, ['value' => $tocache]);
        return $tocache;
    }