How do you test a schema change against the previous release?

A migration can pass with the new build and still break a worker from the previous release that's finishing a queued job. Rename a column in one deploy, and that worker may keep writing the old name after the database has moved on.

Adding the new field first lets both versions coexist. Then you can backfill, switch reads, and remove the old field in a later deploy. The dangerous bit is declaring the old writers gone too early.

What do you check before that cleanup: running worker versions, drained queues, or logs showing no writes to the old field? If you run a small team, what's the smallest check you'd trust?