Explain the reference data you have used.

Reference data is static or slowly changing information that provides context to transactional data. It is used to standardize, validate, and enrich data across an organization. Common examples include country codes, industry classifications, product categories, and currency codes. In my previous role, I worked with reference data for customer segmentation, where I maintained a master list of customer tiers and risk scores. I stored this data in a dedicated reference table in our data warehouse, ensuring it was versioned and audited. When new transactional records arrived, we joined them with the reference table to add descriptive attributes, enabling downstream analytics and reporting. Maintaining reference data involves regular updates, deduplication, and ensuring consistency across systems. I also implemented a simple governance process where changes were reviewed by a data steward before being promoted to production. This practice helped reduce data quality issues and improved the reliability of our analytics.