Comment by hoffcoder

Kafka can be used if you want to treat data as streams for some processing (think producer-consumer kind of scenarios). You can point to the stream from any point in time to read it 'as and when things happened'. Kafka's own nodes have replication enabled, and the data that it produces can be consumed in a distributed setting as well (meaning multiple consumers acting as a single high level consumer). But it is not a traditional database as MongoDB or MySQL.