The document discusses setting up a Scalable Metrics Model (SMM) for a data lake. The SMM uses pre-aggregated metrics and dimension keys to provide a flexible and scalable approach. An example model from retail is described, including defining customer-level dimensions, metrics, and value-added metrics. The document outlines the ETL process, including writing queries to populate metrics for different granularities and integrating them into a framework. Reporting options are also discussed, including using views, tables, and reporting tools to provide accessibility and analysis capabilities. Finally, the extensibility of the model by adding new dimensions like sellers and transactions is highlighted.