Postgres's replication is very good these days, and it works for many of the read-scaling use cases. Scaling writes is a harder problem and I don't think there

Postgres's replication is very good these days, and it works for many of the read-scaling use cases. Scaling writes is a harder problem and I don't think there's a automatic drop-in solution for any sql store that I know of. Mongo gets away with it because it's non-relational so you never have to worry about joining across servers.