System Design
Curated walkthroughs for the bounded designs that show up in real interview loops. Each topic covers requirements, capacity estimation, architecture, deep-dives, and the trade-offs interviewers actually probe for.
URL Shortener
The canonical bounded system design problem. Read-heavy, hot-key prone, and a great vehicle for hashing, caching, and capacity estimation.
News Feed
The classic write-vs-read amplification trade-off. Push, pull, or hybrid fanout - and how to handle the celebrity user with 100M followers.
Rate Limiter
Five algorithms, three sharding strategies, one fail-open vs fail-closed decision. The bounded design that surfaces in every backend interview loop.
Chat
Long-lived connections, ordering guarantees, presence, and the difference between 1:1 chat and a 50K-member group.
Distributed Cache
Consistent hashing, eviction, replication, and what really happens when a single hot key takes down the cluster.
Web Crawler
Politeness, deduplication, freshness, and the URL frontier. The classic crawl-the-internet question that surfaces deep distributed systems judgment.
Video Streaming
Encoding ladders, adaptive bitrate, CDN economics, and the difference between live and VOD. Petabyte-scale storage meets millisecond-scale playback.
Ride-Share Dispatch
Geo-indexing, real-time matching, ETA prediction, and surge. The canonical geo-spatial design problem with hard real-time constraints.
How these walkthroughs work
System design rounds reward depth, not breadth. Memorizing twenty architectures gets you ranked "hire" less often than owning four cold. Each walkthrough is structured the way real interviewers think: clarifying questions first, capacity estimation second, high-level architecture third, then deep-dives into the specific subsystems and trade-offs that decide the score.
Free walkthroughs cover the canonical bounded designs that show up in mid-level loops (URL shortener, news feed). Premium unlocks harder topics that show up at senior+ levels (chat at scale, distributed cache internals). See pricing.
AI-graded practice is coming
Reading is the floor. The next phase wires each topic to an AI interviewer that walks you through a design and probes follow-ups in real time. Want to suggest a topic? Let us know.