If you only do eight, do these
They're ordered by how many of the 100 companies have the problem reported, and 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 guide, reported at 24 companies
- 2Catalog & Search
Inverted indexes, ranking, and latency budgets measured in tens of milliseconds.
Instacart guide, reported at 18 companies
- 3Design a Rate Limiter
Distributed counters and what to do when the counter itself is the bottleneck.
Microsoft guide, reported at 17 companies
- 4Idempotent Payments API
Idempotency and correctness under retries, where "mostly right" is not a grade.
Stripe guide, reported at 17 companies
- 5Design Netflix Video Streaming
Chunking, CDN economics, and degrading quality instead of failing.
Netflix guide, reported at 16 companies
- 6Design the News Feed
Fan-out on write against fan-out on read, and when to change your mind.
Meta guide, reported at 15 companies
- 7Design Uber (Ride Matching)
Spatial indexing and assigning supply to demand while both keep moving.
Uber guide, reported at 12 companies
- 8Design Message Storage at Scale
Partitioning, replication, and the consistency you are willing to give up.
Discord guide, reported at 9 companies
Every system design interview question, by company
Search for a company or a problem, or show only the free lessons. Seeing the same prompt under several companies is a quick way to spot what each one tends to push on.
354 questions across 100 companies.
How to prepare for a system design interview
The building blocks are the same everywhere: caches, queues, partitioning and replication. Knowing them well keeps you from stalling in the first ten minutes, and the System Design 101 course covers them one at a time.
After that, practise the problems your target company tends to reuse. The guides for Google, Meta and Uber are a good place to see how much a company's own products shape its design questions.