System design,
the way it
should've been taught.
Ten step-by-step lessons where the diagram builds itself as you read. Click a step, watch the cache appear, see the traffic move. You leave with a way of thinking, not a slide to memorize.
Sharding, caching, async analytics.
Fan-out, timeline cache, the celebrity problem.
Sockets, offline delivery, group chat.
Used by engineers at
Big systems stop feeling like a black box.
Interview prep, day job, plain curiosity. Same deal. You move through real architectures in order, with a scene that matches the story instead of fighting it.
A scene that moves with the words.
No more boxes-and-arrows screenshots. Read a step, the diagram updates. The cache shows up the moment you need it.
One small idea per step.
No wall of text before you see what changed. Twelve to fourteen steps per lesson, each adding one decision.
Reasons, not just answers.
Tradeoffs are written next to the move that triggered them, so the ordering of choices stays intact.
On the syllabus.
Ten lessons. Twelve to fourteen steps each. Two free, eight pro. Sign in and your place saves between sessions.
System Design Overview
FreeLearn the 6-step design process and explore every core component: clients, servers, databases, caches, and load balancers.
URL Shortener
FreeDesign a URL shortening service like Bitly handling 100M+ daily redirects. Cover key-value storage, caching, sharding, and async analytics.
Twitter (X)
ProDesign a social media platform like Twitter handling 300M DAU. Cover fan-out strategies, timeline caching, message queues, and the celebrity problem.
Design a real-time messaging app like WhatsApp handling 100M DAU. Cover WebSocket connections, offline delivery, inbox caching, and group chat.
Netflix
ProDesign a video streaming platform like Netflix handling 100M DAU. Cover Open Connect CDN, adaptive bitrate streaming, and ML-powered recommendations.
Uber
ProDesign a ride-hailing platform like Uber handling 20M trips/day. Cover geospatial indexing, real-time tracking, driver matching, and trip state machines.
Rate Limiter
ProDesign a distributed rate limiter at the API gateway. Cover token bucket algorithm, Redis-backed atomic state, circuit breaker fallback, and hot key optimization.
TicketMaster
ProDesign a ticket booking platform like TicketMaster handling flash sales with millions of concurrent users. Cover seat locking, virtual queues, and distributed consistency.
Dropbox
ProDesign a cloud file storage and sync service like Dropbox. Cover file chunking, deduplication, delta sync, conflict resolution, and cross-device synchronization.
Yelp
ProDesign a local business search and reviews platform like Yelp. Cover geo-text search with Elasticsearch, CDC index sync, precomputed aggregates, and async review fanout.
Traffic, not clipart.
Nodes show up in order. Requests crawl along the lines. When something gets hot or slow, you see that too. Less guessing what the slide was trying to say.
You're not memorizing one diagram. You're learning where requests live, what breaks first, and which knob you'd turn next.
The same habits transfer when the interview question changes.
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Open the lessons.
Sign in, pick a topic, and your place saves across sessions. Two lessons free, no card required.