Two application versions overlap during a rolling deployment. The new version wants to rename a required database column immediately. Which migration approach best preserves rollback compatibility?

1. Drop the old column before any new application instance starts.
2. Rename the column differently in every environment without recording it.
3. Assume a successful container build makes every schema change backward compatible.
4. Use an expand-and-contract migration: add compatible structure, transition application behavior, and remove old structure only after the compatibility window.