def expired?(service_name)
      if entry = @record_cache[service_name]
        return Time.now > (entry.resolution_time + entry.ttl)
      else
        return true
      end
    end
def expired?(service_name)
      if entry = @record_cache[service_name]
        return Time.now > (entry.resolution_time + entry.ttl)
      else
        return true
      end
    end
Checks if the cached entry for the given service has expired.
 @param [String] service_name the name of the service to check
 @return [Boolean] true if the entry has expired, false otherwise.
                  Always returns true if the record had no TTL.