Quarkus Kafka concurrency

I use quarkus to process incoming messages from Kafka topic that has 4 partitions. While I ingest multiple messages to this topic I see the quarkus-kafka-consumer-code process the message one by one sequentially.

Below is my logic that process the incoming message. Having the topic with 4 partitions should the processEvent method handle 4 messages in parallel as I run only one instance of this consumer-app. Am I missing anything?

@Incoming("topic-1")
@Retry(delay = 3, maxRetries = 3, retryOn = { MyException.class })
@NonBlocking
public CompletionStage<Void> processEvent(KafkaRecordBatch<String, String> payload) {
    Multi.createFrom().iterable(payload.getRecords())
            .onItem().transform(EventProcessor1::newLogEvent).filter(l -> !l.isEmptyEvent())
            .onItem()
            .transform(this::processEvent).onItem().transformToUniAndConcatenate(this::process2).collect().with(Collectors.counting())
            .subscribe().with(c -> {
                log.info("completed {} events", c);
            });

   return payload.ack().whenCompleteAsync((s, e) -> {
        if (e != null) {
            throw new RuntimeException(e);
        }
        log.debug("batch processed & comitted successfully");
    });
            });
}