We use alembic, a python sort of DSL, for migrations. We can go forward or backwards. Any schema changes need an alembic script for both directions. We generall

We use alembic, a python sort of DSL, for migrations. We can go forward or backwards. Any schema changes need an alembic script for both directions. We generally try to do 'mini-migrations' that go with each change, as opposed to big bang migrations. In the past building stock exchanges it was generally big bang with a mass of SQL that could only run once. This are better these days. :)