Creating instant group messaging application

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C#

Well, guys I'm looking to create an instant group messaging application and I'm working on it for two days. Me and my friend are working together to create a best instant group messaging application for our community. It's a gaming community and we want to add a social group messaging on our community. For two or more three days, we're just thinking about MySQL database. We're creating the chat application based on MySQL database and we're thinking to do everything with it. But I'm just afraid of getting fail after time to time because I think that working only with Database will make our application down like because its take some time to load and get data from server to client. I just want your feedbacks that what you think should I continue using MySQL for chat application or should I create a server which will control most of the traffic, I'm not that much pro in this I just create software but creating a chat group messaging is my first time.

So I want to know whats good to use and what we should create to make our application reliable and up always ;)

Also, if you know something about how WhatsApp group messaging work and they're directly using database or a server before database.