Replication Factor
The number of copies of each partition kept on different brokers, defining the topic's fault tolerance.
Replication factor is configured per topic and determines how many replicas of each partition exist in the cluster — one acting as leader and the rest as followers. A replication factor of 3 means the cluster can lose up to 2 brokers holding replicas of that partition without losing confirmed data, as long as the remaining replicas are in the ISR at the moment of failure. Replication factor shouldn't be confused with the number of partitions: one defines how many copies exist of each partition (availability), the other defines how many slices the topic is split into (parallelism and scale).
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