private void processWorkLog() {
        while (runningRequests.size() < getNumberOfConcurrentRequests() && !workLog.isEmpty()) {
            RequestTransaction next = workLog.poll();
            if (next != null) {
                runningRequests.add(next);
                Future<?> completionFuture = executor.submit(next.operation);
                next.setCompletionFuture(completionFuture);
            }
        }
    }
Important, this is a FIFO Queue for Fairness!
plc4j/spi/src/main/java/org/apache/plc4x/java/spi/transaction/RequestTransactionManager.java