You now understand data quality:
- dimensions: completeness, accuracy, timeliness, consistency, validity, uniqueness
- Layer tests: schema, row-level, aggregate, relationship, freshness
- dbt provides built-in testing with simple YAML configuration
- Data contracts formalize expectations between teams
- Great Expectations offers programmatic validation in Python
In interviews, share war stories. Times you caught bad data before it caused damage. The monitoring you built. Quality is about preventing problems, not just fixing them.