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ETL (extract, transform, load)

ETL is a process that extracts data from sources, transforms it, and then loads it into a destination such as a warehouse.

Written by Reflective Data experts · updated Oct 5, 2026

In classic ETL the transformation happens before loading, on a separate server. It was designed for an era when warehouse storage and compute were expensive.

Modern cloud warehouses made it practical to load first and transform afterwards, which led to ELT.

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Data pipelineData warehouseELT (extract, load, transform)

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