[crimsonpowder]

Of course, as soon as an AZ goes down that had all of your Kafka nodes in it, you get eviscerated on HN for running such a setup.

[EdwardDiego]

3 AZ Kafka is the safest, but I've run several 2.5 clusters just fine. (cluster stretched across 2 AZs with a tiebreaker ZK in a 3rd AZ to maintain quorum in the event that you lose an AZ)