What is the workflow logic of Realm React Native?

I discovered Realm for the first time few days ago thanks to this article. So I started to read blogs, tutorials and the official Realm website. Finally I decided to move from SQLite to Realm in our new React Native based cross-platform application.

There are some questions and doubts that I would clarify before getting hands on our projects. I tried some example codes, some taken from your official website and some taken around the Web.

First of all, I still get unclear how is the workflow logic of opening, writing and closing a realm instance.

What about if a realm doesn’t exists at application start? What about if an old realm already exists instead? Will be overwritten?

When I have to close a realm? And other many similar questions.

This article on Medium confused me a bit.

It would be great if there is a state-of-the-art or best practices on how to use correctly Realm in React Native.