System Design Interview Foundations

What you'll learn

System design interviews test a different skill than DSA or LLD: there's no single correct answer, and the interviewer is evaluating your process — how you clarify requirements, reason about scale, and navigate tradeoffs — as much as the final diagram. This course builds the full concept vocabulary every system design answer draws from — from how a request physically reaches your server (DNS, TCP, HTTP) through load balancing, caching, API design, rate limiting, consistent hashing, databases at scale (indexing, transactions, sharding), async messaging, and observability — and then teaches the actual interview framework for turning that vocabulary into a structured 45-minute answer.

This course is the theory companion to the System Design practice bank (/practice?track=SYSTEM_DESIGN) — read a module here, then go work through a named design problem (Design a URL Shortener, Design Instagram's Feed, and others) to apply it. Several modules include an animated, step-through diagram — the DNS resolution chain, a token-bucket rate limiter actually accepting and rejecting requests, a consistent hash ring absorbing a new server with minimal disruption, hash-based shard routing, and a distributed trace's spans — so the mechanics aren't just described in prose, they're shown running.

Who this is for

Anyone preparing for a system design interview round — a format used from mid-level up through staff/principal loops at nearly every tech company — who wants the underlying concepts explained clearly, and shown in motion, rather than memorized as buzzwords.