Just curious if this is a stab at Cassandra, or whether use of Cassandra would automatically imply eventual consistency or something else that would appear in this way?

Cassandra as it's often used can imply eventual consistency (e.g. counter incrs with CL.ONE) but "eventual" in this case would be in the range of 10's of ms

That said, reddit's upvote counters in particular are stored in Postgres, not Cassandra

That one is in postgres