Mongo doesn't really do that in a way you can reliably use in practice either, though. Its sharding offers a subset of operations over an inconsistent view of y

Mongo doesn't really do that in a way you can reliably use in practice either, though. Its sharding offers a subset of operations over an inconsistent view of your dbs. You can do that with Postgres trivially, and even automatically with postgres_fdw and writeable views.