public function catchUpSubscription(
        string $streamId,
        int $startFrom = self::POSITION_START,
        bool $resolveLink = false
    ): Observable {
        return $this->readEventsForward($streamId, $startFrom, self::DEFAULT_MAX_EVENTS, $resolveLink)
            ->concat($this->volatileSubscription($streamId, $resolveLink));
    }