Suppose you have built a data model in the gold layer, and over time the solution has expanded into multiple tables, relationships, and complex logic. An enhancement requires changes to the gold layer. How would you approach this?

I would first review the existing schema and data contracts to understand the current model. Next, I’d create a versioned copy of the gold tables (e.g., using Delta Lake’s time travel) to preserve the original data. I’d design the new schema changes—adding columns, normalizing tables, or denormalizing as needed—while ensuring backward compatibility for downstream consumers. I’d implement the changes in a separate branch or notebook, run unit tests and data quality checks, and then promote the updated models to production via a controlled deployment pipeline. Throughout, I’d maintain documentation of the schema evolution and update any dependent dbt models or BI reports. Finally, I’d monitor the updated jobs for performance and data quality, and roll back if any issues arise.