I see several SaaS companies, such as bitrix have different top level domains by country ex: bitrix.de for germany bitrix.in for india etc.
A lot of times this is required because of legal requirements that the data generated in Germany should stay within the EU/German data center, and vice versa same for India.
My queries
To achieve the above, there would be 1 database + 1 App Server in India, and a similar 1 database + App server for Germany also?
What should happen if a user created an account on bitrix.in ie in the Indian database, and then he goes and tries to accidentally log in to bitrix.com, should such a login go through or should I tell the user that he is on the wrong site?
Tx
You can create a central database for storing meta data - accounts, logins, etc. This could be common/shared across all countries/domains or it could be separate in each database but replicated at a central meta database.
Now when someone logs in, after authentication (using the central meta database) you can redirect them to the appropriate domain.
In such a configuration when creating a new user you will have to ensure that the user is unique across all domains/databases.