The most common question from engineers new to data warehousing is: "Why can't we just scale up PostgreSQL?" The truth is Redshift was forked from PostgreSQL 8.0.2, and SQL syntax is nearly identical. However, a single PostgreSQL instance takes minutes or hours on analytical queries with GROUP BY and JOIN over hundreds of millions of rows. Redshift completes the same query in seconds. The difference is not the SQL engine but the storage structure (columnar orientation) and execution architecture (MPP, distributed). Understanding Redshift means understanding "how data is scattered across nodes and slices, and how queries are executed in parallel on top of that."