There are no hard limits on the number of tables, but every node has a copy of the schema and metadata for every table in memory, so having a huge number of tables could cause memory problems. I’m not aware of any testing that’s been done with more than tens of tables.
I would expect Cockroach to be able to handle more client connections than PostgreSQL itself can, because goroutines are cheaper than the full processes that Postgres uses for its connections. Tools like
pgpool should work to concentrate client connections if it becomes an issue. But again, I don’t think anyone has done any testing for the limits in this area.