It’s a common misconception that you should use processes to structure your application. Instead use modules to organize your application and use processes when you need concurrency or shared state between processes.

I think you should start by considering the external interface of your application, right now it’s a black box so you can design it however you want. But if you add an HTTP interface you probably want to handle requests in parallel, so the web server will start a process per connection or request. So now you need shared state between these processes which can be solved as you proposed, but your solutions are overly complex. Why a process per employee, why not a single process for all employees, or a single process for your whole database?

You should also be careful about using processes to store information that is not transient. You don’t want to lose employee information because the employee process crashed.

Employees, timecard events, schedules, vacations, and overtime may be important concepts for structuring data and possibly even parts of application state but really don’t inform much in terms application behaviour.

Alan Kay (1998)

I’m sorry that I long ago coined the term “objects” for this topic because it gets many people to focus on the lesser idea. The big idea is “messaging” …

This comment highlights how people like to focus in on (static) “objects” because that is comparatively easy when in fact the application value is derived primarily by the (dynamic) “collaborations” that implement application behaviour.

Similarly in a BEAM application the ideal process structure is influenced much more heavily by the behaviour the application is meant to exhibit rather than the structure of the data it is managing or transforming.

This Erlang developer puts a different spin on it:
Lambda Days 2015 - Torben Hoffmann - Thinking like an Erlanger

Processes as the building blocks for protocols - so the big idea is designing protocols realized through communicating processes to implement application behaviour.

This is impossible to answer. If we take your employees as an example, using one process per employee is likely wrong because it’s hard to argue why you should have one process per employee instead of a single process holding a list of employees. You also want to store schedules, should they be stored separately from employees? Possibly, but what would you gain from that?

Eventually you can consider storing the whole database in one process. What are the benefits and downsides of this? One benefit is less complexity, one process is simpler than multiple, another is that you can more easily implement transactions because you don’t need synchronization between multiple process.

One downside can be seen as an code organization, all your database would be in one location, but this is the misconception. Code is organized with modules, so you can have multiple modules for one process. Another downside can be scalability, you may want to shard your database to multiple process so you can use all your cores. This is when you should start considering using multiple process.

So to summarize, it is hard to answer this question because you are asking how to structure an application using processes when we are saying that you shouldn’t. I would suggest that you start writing the application without processes or with a single process and then when you hit a road block that you think processes will solve come back and ask a question that is specific to your problem and less abstract and hypothetical.