I'd be grateful for some comments on the advisability of using a large number of concurrent logical replication publications/subscriptions. Below I've set out the current environment and a suggested design. Apologies for the length of this email.
Another possibility is to use SymmetricDS for this. [ https://symmetricds.org ] SymmetricDS was originally developed to keep databases on thousands of Point-of-Sale databases (in cash registers) in sync with pricing and inventory data for large international retailers.
There are lots of other use cases, but even 10-12 years ago it was scalable to the extent you are describing you need here.
The main drawback is that it is trigger based, so there is some slight latency introduced for insert/update/delete actions on the tables on the appropriate master, but it usually isn't significant.
