SQL instance is fast and for transactional systems - like stock exchange, purchasing something,... called schema on write. DW is for analytics and reporting.

SQL instance is fast and for transactional systems - like stock exchange, purchasing something,... called schema on write. DW is for analytics and reporting. Data Lake is like many DWs together and other, often "garbage" data, which "might" be useful in future analysis, ML and stuff. It's the unstructured graveyard of data (joking). Schema is defined on read.