What you need to know
Application instances may deploy at different times, and a migration can fail after some work has completed. A staged plan reduces the chance that a release leaves the app unable to read its data.
How to apply it
Add compatible fields first, deploy code that can read both shapes, backfill in batches, switch writes, then remove obsolete fields in a later release. Keep a clear pause or rollback path.
Common mistake to avoid
Do not combine a destructive migration and an application release that immediately requires it. Preserve recoverability until the new path is verified.