Schema Evolution

Concepts: paTableFormats

What They Want to Hear 'Schema changes are inevitable. My approach: adding a nullable column is always safe. Widening a type (int to long) is safe. Removing a column or narrowing a type is a breaking change that requires a migration plan with dual-write during the transition.' Then mention table formats: 'Iceberg and Delta handle safe schema evolution natively. For breaking changes, I use a dual-write period where both old and new schemas are produced simultaneously.'