I have a setup where two Odoo 16 databases are hosted on the same server, each accessed through separate domains and separate Odoo installations. The user wants real-time synchronization of products and inventory between both databases. 
Specifically:
a) The same set of products should exist in both databases. 
b) Any inventory change (inbound or outbound) in one database should automatically update the stock level in the other. 
c) At any point in time, stock levels must remain consistent across both systems. 

What is the best technical approach to implement this real-time, two-way synchronization of products and inventory between these two Odoo instances?