Did they make the move to ScyllaDB, as mentioned in their "Future work" section?

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

Still a good read if you're curious about Cassandra

2017 is pretty antique though now: the scaling and the ecosystem change fast

I admittedly know very little about this space. What are some of the newer players?

If you are not familiar, DB-engines.com keeps a listing of who the major players are in the database world.

https://db-engines.com/en/ranking

MongoDB is ranked #5 on the list at present; Cassandra comes in at #11. (And Scylla, which they moved to most of their workload from Cassandra, is currently #88.)

DB-engines also have specific rankings for what are known as 'NoSQL wide column stores' — which is what Cassandra and Scylla are classed as:

https://db-engines.com/en/ranking/wide+column+store

Note that MongoDB is a different class of NoSQL entirely. It is a "document store" — MongoDB is the most popular document store.

https://db-engines.com/en/ranking/document+store

But what this means is that even though both MongoDB, Cassandra and Scylla are all "NoSQL" making this move for Discord required significant data modeling and migration.

(Note that the difference between Cassandra and Scylla is far narrower. Both use the same data model and Cassandra Query Language (CQL).

Hope that helps give you some orientation in the NoSQL database field.

This is excellent. Thank you!

Scylla, for one. Which is mentioned as a possible "next step" in the article.

...then [post this blog] Scylla.

https://www.scylladb.com/press-release/discord-chooses-scyll...