In my service, I have used one of distributed DB, vitess from beginning. The problem was spending too many time for every time make table and shard key design to avoid placing a heavy load for DB with join, broadcast query, and so on.

I’d like to recommend If you are really need to scale out soon, your domain is difficult to separated, only use distributed DB.

It is true, distributed databases superior to many people technically, But that’s not mean they are better in your service situation

I think it is better spend your time, separate domain architecture. Simply use DB. Do not put unpredictable future off DB as past Oracle DB handle all.