So lets say you have a team that handles user on-boarding and account management. If you want a top bar with the user name, does this feature have to be owned by the user account team? If they're different teams with different microfrontends, how does the top bar frontend know to update based on activity in the account management frontend?
Basically, cross vertical information will exist, how do you solve the caching problems? Maybe some kind of app wide message passing?
In lots of cases, one view is one micro-front-end. The split is not header-body-sidebar, but whole pages. I saw a talk from DAZN-engineering about this topic [1].
Just like in Marvel-Movies, where the countless VFX-Companies produce entire scenes, not just parts of it.
If you are using react/redux it would be a rather trivial matter of defining an action/state tree contract between the teams. Other frameworks that use encapsulated state may have to resort to a message bus.
Edit: I misunderstood the context. If your front ends are separate applications this won't work.
Having that kind of tight coupling (not only interfaces, but also libraries beyond the minimum you need for core things like the design system) partly defeats the purpose. If you have a lot of micro apps and they share dependencies/frameworks, you won't get the benefits of eventual consistency when the next big thing comes along.
For something like onboarding, any team handling that will either just be a "think tank" (PMs/Designers working with the actual owners of the individual affected apps to build the experience), or will be people who jump in other folks' code bases to implement it. Alternatively, they could only be responsible for building a suite of components that the app owners bring in their apps to glue things together.
Basically, cross vertical information will exist, how do you solve the caching problems? Maybe some kind of app wide message passing?