Build it: Design a URL Shortener
An interactive sandbox where you drag real components together, connect them, and run a live traffic simulation to see where the design breaks.
Challenge: Design the read path for a URL shortener. The user sends <strong>150 redirects/sec</strong>. Each app server handles <strong>40 r/s</strong>; the database only <strong>30 r/s</strong>. Most reads are for the same hot links. Build a system that serves all 150 r/s without melting the database.