How to organize the relevance and integrity of data in the database?

Question

Database

Good day to all and Happy Valentine's Day, who are celebrating!
There was a project to create a personal user account and the following question appeared:
How to organize the interaction of a database with a web application on ASP.NET? And it's not about ConnectionString, etc., but about the architecture. Suppose there are the following options:
1) For example, the application "kicks" the SQL server for changes every, well, for example, a minute and pumps out these changes (how can this be arranged? Moreover, so that incorrect data is not sent to the database)
2) Using the package, every at night, the data is unloaded into the database of the office from the remote database, they are corrected and loaded (but there is a problem, the data will be lagging a day, every time)
3) ... I don’t know, please suggest)
I am sure that I am not the first to encounter such a problem, I would like to hear an answer from experienced people, maybe there is some kind of pattern of such interaction.
The important thing is that it would be better if the data were up-to-date at every moment of time, so that it would be fault-tolerant (in case the table structure was changed and, for example, a column was removed in one of the main tables), and that it all worked stably.
Thank you all in advance!

Answer 1

Entity Framework+DataAnnotations+DataValidation+Migrations

Answer 2

If you want relevance, then you can’t get away from polling.
Here, rather, you need to think about how to correctly organize polling and how to guarantee the availability of the database (if IIS and the database are on the same server, there are no problems).
Try to send as little data as possible - look towards AJAX+JSON.
Update only the most important data, the rest separately at the user's request (i.e. make an overview page and a few specialized ones).
I didn’t understand about fault tolerance - if a column was removed from the table, then the application needs to be adapted. How else?