In my previous post, I explained how a disk attached to a machine makes things difficult. Vertical scaling has its limits, and when you hit that limit, you can’t do horizontal scaling right away because of the attached disk. Mainstream databases like Postgres or MySQL don’t scale horizontally. I recently learned that BlueSky team switched from Postgres to a combination of Scylla and SQLite. One of the reasons was because (vanilla) Postgres is not horizontally scalable, but Scylla is.