ETL (Extract, Transform, Load): Transform data before loading. Traditional approach. Required when target systems have limited compute.
ELT (Extract, Load, Transform): Load raw data first, transform in warehouse. Modern approach. Use cloud warehouse compute power.
ELT won because:
Cloud warehouses have cheap, elastic compute
Raw data preservation enables reprocessing
dbt makes in-warehouse transforms maintainable
In interviews, explain why ELT is now standard while acknowledging ETL still makes sense for legacy systems or specific compliance requirements.