When reading from the dataframe, depending on the columns, filters, and aggregates you want returned, most query engines can skip data that is irrelevant, makin

When reading from the dataframe, depending on the columns, filters, and aggregates you want returned, most query engines can skip data that is irrelevant, making the query run much faster. In your amazon example the data is probably optimized for fast lookups on a small number of records, like an in-memory cache.