Comment by kbenson

For what it's worth, I think distributing horizontally is also much easier if you're already limited your database to specific concerns by splitting it up in different ways. Sharding a very large database with lots of data deeply linked sounds like much more of a pain than something with a limited scope that isn't too deeply linked with data because it's already in other databases.

To some degree, sharding brings in a lot of the same complexities as different microservices with their own data store, in that you sometimes have to query across multiple sources and combine in the client.