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ELT (Extract, Load, Transform)

A modern data integration pattern that loads raw data directly into a target system first and then transforms it in place, leveraging the processing power of cloud data warehouses.

ELT reverses the traditional ETL order. Raw data is extracted from sources and loaded directly into a cloud data warehouse (Snowflake, BigQuery, Redshift) without transformation. Transformations then happen inside the warehouse using SQL, leveraging the warehouse's massive parallel processing capabilities.

This approach became practical with the rise of cloud data warehouses that offer virtually unlimited compute for transformation. Tools like Fivetran and Airbyte handle the extract-load phase, syncing data from hundreds of sources into the warehouse. dbt (data build tool) then handles the transform phase, applying SQL transformations with version control, testing, and documentation.

For AI teams, ELT offers flexibility. Raw data is preserved in the warehouse, so new features can be computed from historical data without re-extracting from sources. Data scientists can experiment with different transformations using SQL before productionizing them as dbt models. The approach also supports schema evolution more gracefully, since raw data is always available for reprocessing when requirements change.

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