public boolean isExpired(long timeoutMs) {
        return System.currentTimeMillis() - lastHeartbeat > timeoutMs;
    }

    // Getters and setters

    /**
     * Gets the last heartbeat timestamp.
     *
     * @return the last heartbeat timestamp in milliseconds
     */
    public long getLastHeartbeat() {
        return lastHeartbeat;
    }

    /**
     * Gets the registration ID.
     *