Is it possible to write data directly to a specific Kafka partition, bypassing the hash key?

In Apache Kafka, you can specify the partition number directly when sending a message, bypassing the use of a key for hashing. When creating a message (ProducerRecord) in the Kafka Producer API, there is a parameter called partition, which allows you to explicitly specify which partition the message will go to.

If you specify the partition, the hash key is not used to select the partition. This is useful when you need to manually control the distribution of messages across partitions.

Example in Go using the sarama library:

msg := &sarama.ProducerMessage{
    Topic:     "my_topic",
    Partition: 2, // explicitly specify the partition
    Value:     sarama.StringEncoder("message"),
}
producer.SendMessage(msg)

Thus, you can directly write data to a specific partition if the library and API you are using support it.