I am using Swift as a programming language and Firebase for my backend.
My use case is about creating an event (a tournament) which has different rounds (RoundOf16, Quarter-Finale, Semi-Finale etc.)

Whenever a new rounds starts and finishes, I want to send out notifications to the participants. It would be easy to do that by using local notifications.

However, additionally to sending the notifications, I also want to trigger a function to check if a participant can make it to the next round or if the event has even enough participants to start.

How can I do that? Is there a client-side way to achieve this or can it only be done server-side? The functions would need to run completely in the background as it is the case that you close the app, even though the round is still active.