protected function store_redis_cache_write(
		$token, $data, $expire_at, $expire=null
	) {
		if (!$this->redis)
			return;

		$key = sprintf('%s:%s', $this->token_name, $token);
		$this->redis->set($key, json_encode($data));

		if ($expire === null) {
			$expire_at = str_replace(' ', 'T', $expire_at) . 'Z';
			$expire_at = \DateTime::createFromFormat(
				\DateTime::ATOM, $expire_at)->format("U");
			$expire = $expire_at;
		}
		$this->redis->expire($key, $expire);

		$this->logger->debug(sprintf(
			"Zapmin: session written to cache: '%s' <- '%s'.",
			$token, json_encode($data)));
	}