Model/Config/ConfigRewrite.php
public function afterSave(\Magento\Config\Model\Config $subject) // @codingStandardsIgnoreLine - unused parameter
    {
        if ($this->purge) {
            $this->api->cleanBySurrogateKey(['text']);
        }
    }
public function afterSave(\Magento\Config\Model\Config $subject) // @codingStandardsIgnoreLine - unused parameter
    {
        if ($this->purge) {
            $this->api->cleanBySurrogateKey(['text']);
        }
    }
Trigger purge if set

@param \Magento\Config\Model\Config $subject
@throws \Zend_Uri_Exception