public function existsItem(string $key): bool
    {
        if (!$this->adapter instanceof iAdapter) {
            return false;
        }

        $storeKey = $this->calculateStoreKey($key);

        // check static-cache
        if ($this->checkForStaticCache($storeKey)) {
            return true;
        }

        return $this->adapter->exists($storeKey);
    }