Clearly, Kafka has to replicate the events across multiple broker machines because a bomb can destroy the building where the data was stored.
The events are what I need replicated. Kafka implements replication at a partition level. A partition gets replicated into N brokers.
Leader replica and follower replica
For a particular partition, the leader replica of the partition is where the writes happen first. There after, the data gets copied into the other replicas, and these replicas are called follower replicas.One broker would host leader replicas for some partitions, and follower replicas for other partitions.
Replication is automatic as long as the replication is turned on. Developers do not have to think about it typically. There are options for tuning replication while writing into a topics should a specific requirement arise.
