Back in 2014 when i last used Cassandra, Netflix were using it for some kind of metrics store i believe. They also published the nicer-to-use client back then (astyanx or something it was called - nicer API than Hector).

My memory is letting me down here on specifics - in my defence it's been a long time since i answered questions on stack overflow about Cassandra. I absolutely loved working with the product even if the sharp edges cut me a few times (ultimately my own fault not Cassandra's).

Netflix uses it for everything that you'd use Postgres for but:

- they have Cassandra committers (most end up going to Apple iCloud)

- they have mgmt. support to make it work

- they are/were on tokens for years, not vtokens, since their internal tools were token-based

(They started with Oracle Enterprise (and a little MySQL), tried Mongo briefly, then decided to make Cassandra work for them.)

Source: original Netflix Cassandra team member.