yoyo if raw SQL in the app, Alembic if it uses SQLAlchemy

can you recommend how to approach migrations when you already have a database in place, rather than starting from scratch?

The current state before you make the migration is the baseline, that’s in. Any further changes should only be done with a migration file. Talk to the team, give a tech demo and revoke everyone’s write access to the prod DB.

SQLAlchemy + Alembic, nicely wrapped in Flask-SQLAlchemy and Flask-Migrate. Flask-SQLAlchemy is not compatible with type annotations, so you’ll need a workaround. Here’s mine.