Someone wrote a guide on how to design Twitter.
Then how to design Instagram.
Then how to design Uber.
Then how to design TinyURL.
Then how to design Amazon's product catalog.
Then how to design YouTube.
Then how to design a web crawler.
Then put all of it on GitHub. For free.
Not a snippet. Not an overview. A complete deep-dive into every major system design interview question with diagrams, trade-offs, scaling strategies, and architectural decisions explained in detail.
It is called the System Design Primer. 312,000 stars on GitHub.
Built by Donne Martin, a former Facebook engineer who got tired of watching candidates fail technical interviews because nobody had taught them how to think about scale.
Here is what is inside.
How to design a URL shortener.
How to design Pastebin.
How to design Twitter.
How to design a web crawler.
How to design Mint.
How to design Amazon's sales rank system.
How to design a key-value cache.
How to design a social network feed.
How to design a notification system.
How to design a chat system.
How to design a search engine.
How to design Uber.
How to design Instagram's photo upload pipeline.
How to design YouTube's video streaming.
How to design Reddit's voting system.
Each one includes:
Functional and non-functional requirements.
Capacity estimation.
System interface definitions.
Database schema design.
High-level architectural diagrams.
Deep-dive trade-offs on consistency, availability, and partition tolerance.
Cache strategies.
Load balancing approaches.
Database sharding decisions.
Real-world bottlenecks and how to solve them.
Plus a complete reference section on the underlying concepts, CAP theorem, eventual consistency, CDN architecture, microservices, message queues, MapReduce, distributed databases, replication strategies, consensus algorithms.
Here is why this matters.
System design interviews are how Google, Meta, Amazon, Netflix, and every major tech company decide who they hire for senior engineering roles. A single failed system design interview can cost you a $300,000-per-year job offer.
Interview prep companies charge $2,000 to $5,000 for system design coaching. Books on the topic cost $50 to $100 each.
This repo gives you all of it. For free. Updated continuously by the community. Translated into 8 languages.
Here is the wildest part.
The people getting hired at top tech companies are reading this repo. The interviewers asking these questions are using this repo to design their interview rubrics. The hiring managers reviewing candidates are checking whether the answers match what is in this repo.
The entire system design interview industry runs on knowledge that is freely available in one GitHub repository.
312,000 stars. CC-BY 4.0 license.
The interview prep industry: $2,000 to $5,000 per candidate.
Books: $50 to $100 each.
Bootcamps: $15,000.
System Design Primer: $0. Same content. Better organized. Updated weekly.
Every senior engineering role at every major tech company. Solved in one repo.
(Link in the comments)