Kafka Characteristics

Kafka's speed does not come from one trick. It comes from how it uses the disk, the network, and the operating system together. This lesson looks at where that speed comes from and how long Kafka keeps a message. It also looks at how Kafka stops one heavy client from crowding out the rest.

Storing messages to disks

Kafka writes every message to local disk. It keeps nothing only in RAM. A message that lives only in memory disappears if the broker dies and restarts. Disk storage is what makes messages durable.

Disks have a reputation for being slow, but that depends on the access pattern