Django website - no such table: django_session

Hello,
using DEBUG=True, I was able to see why I had a 500 error. It was a db problem (I don’t use any, but I forgot about request.session for the dark mode, so it is used). Anyway, I was able to use fly ssh console to make migrations, migrate and create a super user. It finally worked. I come back an hour later, and the problem is back. So, I reconnected to the console, made migrations, migrated and created a superuser. Again. It works. But I don’t understand how the whole thing works. How to sqlite database work ? It works fine in development, do i need to run these each time I deploy ? What if I actually had data in the website ? This is concerning.