code: function checkCache (config, pattern) {
  	if (!useCache(config)) {
  		return RESPONSE_UNKNOWN;
  	}
  
  	const valueRetrieved = kvGet(config, pattern);
  	if (valueRetrieved === RESPONSE_UNKNOWN) {
  		return RESPONSE_UNKNOWN;
  	}
  	/* Check if the cache entry has expired. */
  	const lastValidDate = new Date(valueRetrieved.validUntil);
  	if (lastValidDate <= Date.now()) {
  		/* The cache entry has expired. */
  		return RESPONSE_UNKNOWN;
  	}
  	return valueRetrieved.response;
  }
docs: /* Returns RESPONSE_{VULNERABLE|SAFE} on hit, else RESPONSE_UNKNOWN on miss or disabled.