Depends on the database, in my opinion. Each one has quirks to be mindful of, depending on the amount of data you're migrating/touching.

For example, if you accidentally put a 'default' on a column when you add it to postgres, it will lock the entire table while it rewrites every row, inserting that default value.

Another common postgres blunder is creating indexes on big tables without using 'concurrently'. This also locks the table for writing and you'll have a bad time.