I know scalability is not an issue in Firebase and supports up to 100k Simultaneous connections(in general).
Based on pricing documentation:
You can create multiple database instances to go beyond the 100K concurrent limit. See Pricing FAQ for more information.
Question 1: What if there is more than 200k users using simultaneously on the same database? The other half of the users could not query, connect or the request will be placed in queue? (As a Firebase plan subscriber, I would like to know how Firebase deals with the problem to ensure the quality of the services provided to our customers are always in top-notch)
Since, App globalisation is common nowadays and many companies' practices are to have servers across multiple regions to provide better and stable performance. Online game for example which required low latency.
As for now, the firebase user is required to set the default location when creating the project which is non-editable afterward. Some issues even rises where the users realised they deployed their app to the wrong regions and do not have clues on how to change the regions.
This represents the country/region of your organisation/company. Your selection also sets the appropriate currency for your revenue reporting. The selected country does not determine the location of your data for Firebase features. Google may process and store Customer Data anywhere Google or its agents maintain facilities.
Question 2: Will or does Firebase provide a solution / tailor-made to such practice which having our database in multiple regions while having a headquartered region and multiple other regions sharing all the databases, functions and auth across the regions?
(For now to have multiple servers location, we have to create different projects and the user and data syncing will be a problem)
Hope the language does not offend, cheers!