Introduction

Data-Intensive Systems: How to Read This Module

Everything so far served requests: a user asks, the system answers, milliseconds pass. This module serves questions about everything that ever happened: revenue by hour, fraud patterns across millions of orders, features computed over a year of behavior: questions whose input isn't a request but a river: the clickstream, the order events, the change history of every table. Data engineers live here full-time; every other engineer visits weekly, usually by following the question "where does the dashboard's number come from?"