We've moved quite a few datasets from Cassandra to Scylla, but not messages. I think we're planning to make a blog post about our experience with Scylla at some point.

Definitely lemme know when you are going to do that! (peter@scylladb.com here).

Their jobs pages (e.g. [0]) mention "ScyllaDB/Cassandra".

[0] Senior Site Reliability Engineer: https://discord.com/jobs/4004051002

Also:

https://discord.com/jobs/5411664002

https://discord.com/jobs/5426301002