System Design 101
The System Design 101 course teaches you how to design scalable, reliable systems and pass the system design interview: worked end to end, from the fundamentals to full designs of the systems companies actually ask about.
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The System Design Interview
What Interviewers Actually Evaluate
Start with the framework that works on any design question
Course Curriculum
Now design something real.
354 questions actually asked at 100 companies. The same problem is a different interview at each one: a rate limiter is a distributed systems question at Cloudflare and a billing-correctness question at Stripe. Start with whoever you are interviewing at.
If you only do eight, do these.
Ordered by how many of the 100 companies have the problem reported, and picked so each one tests something the others don't. All eight are free to read.
- 1Design Real-Time Multiplayer Editing
Persistent connections, presence, and merging edits from clients that disagree
Figma · reported at 24 companies
- 2Catalog & Search
Inverted indexes, ranking, and latency budgets measured in tens of milliseconds
Instacart · reported at 18 companies
- 3Design a Rate Limiter
Distributed counters and what to do when the counter itself is the bottleneck
Microsoft · reported at 17 companies
- 4Idempotent Payments API
Idempotency and correctness under retries, where "mostly right" is not a grade
Stripe · reported at 17 companies
- 5Design Netflix Video Streaming
Chunking, CDN economics, and degrading quality instead of failing
Netflix · reported at 16 companies
- 6Design the News Feed
Fan-out on write against fan-out on read, and when to change your mind
Meta · reported at 15 companies
- 7Design Uber (Ride Matching)
Spatial indexing and assigning supply to demand while both keep moving
Uber · reported at 12 companies
- 8Design Message Storage at Scale
Partitioning, replication, and the consistency you are willing to give up
Discord · reported at 9 companies
27 questions across 8 companies.
Common questions
What does the System Design 101 course cover?
Four parts. The interview itself: what interviewers actually score, and a delivery framework that works on any prompt. The fundamentals: networking, APIs, data modeling, databases, caching, load balancing, message queues, replication and the CAP theorem. A toolbox of the specific technologies worth naming, from PostgreSQL and Redis to Kafka and Cassandra. And a scaling playbook for reads, writes, contention and real-time updates.
How do I prepare for a system design interview?
Start with a repeatable method so you are not improvising in front of an interviewer: scope the requirements, estimate the load, sketch the high-level design, then go deep where it matters. The course teaches that framework first, then you practise it on the questions companies actually ask.
Is the system design course free?
The interview method and the opening fundamentals are free to read. Premium unlocks the deeper fundamentals, the full toolbox and the scaling playbook.
What system design questions do companies ask?
The same prompt is a different interview at each company: a rate limiter is a distributed-systems problem at Cloudflare and a billing-correctness problem at Stripe. You can browse 354 real questions across 100 companies and practise the ones you are interviewing for.