ETL & ELT Pipelines, Explained

What a data pipeline actually is, the difference between transforming before or after you load, and what it takes to make a scheduled pipeline run reliably instead of just running.

1. Extract, Transform, Load A pipeline is an assembly line with three stages: extract pulls data from sources, transform cleans and reshapes it, and load writes it where people use it.
2. ETL vs ELT ETL transforms before loading (the classic order, born when compute was scarce); ELT loads raw data first and transforms it inside a powerful cloud warehouse - preserving the raw data and letting you transform with SQL.
3. Orchestration: Making It Run Reliably A real pipeline is a scheduled, multi-step job: dependencies form a DAG, steps run on a schedule with retries, and steps must be idempotent so re-runs and backfills don't double-count - because 'it ran' is not the same as 'it ran correctly.'