How does the bot determine which content to send to whom?

Question

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Let's say I want to make a bot on the platform https://dev.botframework.com/ With the following functionality: take the content of the Vkontakte group and send it to the bot.
Explain the architecture how to do it right.
Let's say it will be a C# application that will take content and send it to the bot.
Is it possible to do without a database? Apparently, if without a database, then the user will see only those posts that were made in the group when he had the messenger running?
And if you make an application with a database, how will it understand which post from which user was loaded last? (because phones are turned off, etc.).
In general, the problem is: there is a VKontakte group on the one hand, and many instant messengers on the other, and between them there is an application. How should it be designed?

Answer 1

In VK, each user / page / group has its own posts. Base or not, you can check the user's latest post, and send him all posts that are newer than this.

Answer 2

The database can store the numbers of posts that the user requested.
Also, the user can, in each request, indicate which posts he has already received