>Some NoSQL databases handle it without Zookeeper.
Most NoSQL databases, now, use Raft, which didn't exist at the time when Kafka was created. Other NoSQL databases, at the time, were not as stable as Zookeeper or had silent bugs that ate data (see aphyr's Jepsen series[1], which thourghly tested several NoSQL databases and found many to be failing, except for Zookeeper).
> Yeah! I mean, I find a lot of linearizability errors in various databases, but this was also my very first time doing this kind of test, and it varies from system to system. Could have easily slipped through the cracks.
In summary, aphyr thought Zookeeper is linearizable even though it doesn't provide linearizable ops.
Most NoSQL databases, now, use Raft, which didn't exist at the time when Kafka was created. Other NoSQL databases, at the time, were not as stable as Zookeeper or had silent bugs that ate data (see aphyr's Jepsen series[1], which thourghly tested several NoSQL databases and found many to be failing, except for Zookeeper).
[1] https://aphyr.com/tags/jepsen