...It teaches readers how to break broad product requirements into components, data flows, storage choices, scaling strategies, and operational tradeoffs. The examples cover URL shortening, news feeds, search engines, crawlers, key-value stores, distributed identifiers, task schedulers, file-system caches, and load balancers. Additional material discusses API rate limiting, hash maps, PageRank, frequent-item analysis, and big-data scenarios. The repository presents each case as a focused Markdown chapter with diagrams and supporting explanations. A methodology chapter helps readers apply a repeatable approach instead of memorizing isolated answers. ...