Observable/Reactive var between multiple projects

As a myVar in my “project1” is observable/reactive, and can make the listeners of that myVar in other projects, “project2”, “project3”, etc…

how this will work in such cenario?
can use that way?
i can seek in a database to initialize properly each of the myVar instances, and fetch against database after each change???

whats the best solution with many projects looking at same Observables/Reactive?