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Inspired by Alex Xu's System Design Interview · start freeInteractive lessons where you crash servers, fill caches and shard databases. Practice that brings back what you got wrong. And an interview simulator that grades your architecture the way an interviewer would.
Not sure where you stand? Take the 3-minute readiness checkRequests flow through a load balancer to three stateless app servers.
Drag in load balancers, caches, queues and databases. Set your own traffic, crank it up to 1000×, crash a server and watch what holds. Every design gets a grade from S to F, and the fixes worth making first.
Inspired by Alex Xu's System Design Interview books, rebuilt as something you can watch, break and practise, with a coach beside you. Written from scratch; not affiliated with the author.
Reading about distributed systems is easy to forget. Seeing them work, breaking them, and then designing one under a timer is not.
Every concept is an animation you control. Step through a request, then break things: kill a server, overflow a queue, lose a replica, and see what happens.
Questions on concepts, trade-offs and back-of-the-envelope maths. Anything you miss comes back on a spaced schedule until you get it right on a later day.
Design Instagram, YouTube or Uber on a canvas in 45 minutes. Get a rubric-based score with evidence, what you missed and the follow-up questions an interviewer would ask.
These are actual lessons from the course, running right here. Press Play, then use the buttons under the diagram to break things.
A load balancer spreads incoming traffic across a group of web servers, and routes around one that fails.
One path from first principles to a full mock interview, with feedback at every step.
Draw the architecture, write requirements, estimates and trade-offs, then submit. Components only count when they're connected, flows must really exist in your diagram, and concepts must be explained. Reasonable alternatives earn credit.
188 questions. Miss one and it returns after 1, 3, 7 and 16 days until it sticks.
Your read-heavy API's database sits at 90% CPU. What's the best first fix?
Caching hot reads removes most database load for the least work. Sharding is a bigger step you take when writes or data size outgrow one machine.
Build a token bucket, a hash ring, a Snowflake ID generator. Your code is checked instantly.
Mastery per chapter, streaks, weak spots and an interview-readiness score built from what you've actually done.
Hints and explanations tied to the lesson, question or design stage you're on.
Run the problem's real traffic through the diagram you drew. Every component fills up as it gets busy. Then throw a viral spike, a dead database or a bot flood at it, fix what breaks, and run it again.
Estimate it, put it in order, spot the bottleneck or pick the tool. The same puzzle for everyone, with a result you can share.
The real round is a conversation. Speak your design to an interviewer who answers your clarifying questions, asks one thing at a time, pushes back on weak spots and keeps time. Then see exactly what you covered and what you missed.
12 questions, about 3 minutes, no sign-up. Get your level and the areas to work on first.
Every problem has a model answer that draws itself step by step and says why each part is there. Then it lists what interviewers listen for and the numbers to estimate, so you learn the whole answer, not just the picture. Copy it to your canvas and try to break it.
Every weak spot in your rating comes with its fix. Apply it in one click and watch the grade move, or let it show you exactly which setting to change.
Follows the chapter order of System Design Interview, Vol. 1, adds six modules on the core concepts every design relies on, and has started on Volume 2. Everything is explained in our own words, so you don't need the books.
Start in guided mode with ten coached stages, then switch to interviewer mode: 45 minutes, no hints, scored at the end.
Try the first chapters, two mock interviews and the whole question bank for free. Pro unlocks everything else.
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₹299for 30 days
or ₹1,999 for a full year (save 44%)
One-time payment through Razorpay (UPI, cards, net banking). Doesn't renew automatically. Non-refundable: refund policy.
Plans, payments, and how the course and the interview simulator work.
Starting is free, with no card: the first three chapters, two interview problems, the full question bank, flashcards and the Daily Design puzzle. Pro unlocks everything for ₹299 for 30 days or ₹1,999 for a year. It's a one-time payment that never renews by itself.
Payments are non-refundable, because Pro unlocks all the content straight away. That's why so much is free to try first. A duplicate or failed charge is always returned. See the refund policy.
No. Every lesson is self-contained and written from scratch. The course follows the chapter order of System Design Interview, Vol. 1 by Alex Xu, so if you own the book the two pair well.
Engineers preparing for system design interviews, from first-timers to seniors who want a structured refresh. Part 1 assumes only basic web knowledge: what a server, a database and an HTTP request are.
With a transparent rubric for each problem. Components count only when they're wired into your diagram, flows must exist as real paths, concepts must be explained in your notes, and estimates are graded by order of magnitude. Reasonable alternatives (say, SQL instead of NoSQL) earn credit when you justify them. The report shows the evidence for every point.
Without an account, progress stays in your browser. Create a free account and it's saved to your account instead, so it follows you to any device. Guest progress is carried over when you sign up.
Lessons, animations and practice work on phones and tablets. The design canvas in the interview simulator is easiest on a laptop.
About 18 hours of lessons. The suggested learning path spreads them over 12 weeks at an hour or two a day, with daily review and a mock interview each week. You can go faster.
Lesson 1 takes about five minutes. You'll see a single server turn into a system that serves millions.
