Django - backend logic vs database logic
It is true that if you used a database for your business logic you could get maximum possible performance and security optimizations. However, you would also risk many things such as 

No separation of concerns
Being bound to the database vendor
etc.

Also, whatever logic you write in your database won't be version controlled with your app. Thus, whenever you change your database, you will have to create all those things once again.
Instead, use Django ORM. It will create and manage your database based on your models by itself. As a result, whenever you recreate your database, you will just have to run migrations with one single command and you are done.
This will cover most of the situations. And whenever you will need those speeds of stored procedures, Django ORM has you covered as well.
In short, I believe that business logic should be kept out of the database as much as possible.
I wonder if a good habit is to have some logic in MySQL database (triggers etc.) instead of logic in Django backend. I'm aware of fact that some functionalities may be done both in backend and in database but I would like to do it in accordance with good practices. I'm not sure I should do some things manually or maybe whole database should be generated by Django (is it possible)? What are the best rules to do it as well as possible? I would like to know the opinion of experienced people.