How to ensure message processing order in Kafka?

In Kafka, the order of message processing is guaranteed within a single partition. To ensure processing order:

• Use one partition for the message key so that all messages with the same key go to the same partition.
• Consumers should process messages from a partition sequentially, not in parallel.

In Go, using a Kafka client (e.g., sarama), you can configure the consumer to process messages from a partition in the order they arrive:

// Example of simplified sequential reading from a partition
partitionConsumer, _ := consumer.ConsumePartition(topic, partition, sarama.OffsetNewest)
for msg := range partitionConsumer.Messages() {
    processMessage(msg) // Process in order
}

If you need to scale processing but maintain order, you can use keys for routing messages to partitions and process each partition in a separate goroutine.