System Design Notes: An Open Companion to a Classic Book

TL;DR: This repository collects notes on the book System Design Interview: An Insider’s Guide by Alex Xu and publishes them free, with no license declared. At 24,674 stars and 4,608 forks, it is one of the most-cloned study resources in backend interview prep, and it is worth reading alongside the book rather than as a replacement for it.

What it is

The repository describes itself plainly: notes on the book System Design Interview: An Insider’s Guide. That is the whole pitch. Someone read a paid, published technical book, took structured notes, and put them on GitHub where anyone can read them.

The homepage link points at a rendered version of the same notes hosted on Vercel, so you can read them in a browser or clone the repository and work through them locally in Markdown.

This is a study resource, not a tool. There is nothing to install, no runtime to configure, and no code to ship. That category of repository is easy to dismiss and easy to underestimate, because the value sits in the reading rather than the artifacts.

The numbers

Metric	Value
Stars	24,674
Forks	4,608
Primary language	Not detected
License	None declared
Created	December 24, 2024
Last push	August 12, 2026
Maintainer	Individual account

Two figures stand out. The repository is under two years old and already has nearly 25,000 stars, which tells you how saturated the system design interview market is. And the fork ratio, roughly one fork per five stars, reflects how aggressively people clone a Markdown resource to annotate, fork for their team’s onboarding, or reformat into their own study system.

GitHub reports no detected primary language, which is consistent with a notes-only repository containing prose and Markdown rather than code.

Why it keeps trending

System design interviews are a fixed part of backend and full-stack hiring loops, and the recommended prep path has not changed much in years: read the canonical book, then grind practice problems. What has changed is that a free companion to step one now exists.

The notes are valuable in a specific way that summaries usually are not. They are organized to the structure of the book itself, so if you have the book you can use them as a checklist for what you actually retained. If you do not have the book, they give you the vocabulary interviewers expect you to use, which is arguably the part that matters most when someone is deciding between two candidates in the last twenty minutes of a call.

The license question, and why it matters here

This is the one detail worth reading carefully. The repository has no declared license.

For a repository full of prose and no code, that distinction is smaller than it would be for a software dependency. You cannot realistically enforce copyright on study notes you published yourself, and nobody is going to come after you for personal study use. But “no license” is not the same as “public domain” or “do what you want.” Under default copyright, the author retains all rights, and the absence of a license means you technically have no permission to redistribute, republish, or fold large portions into your own material.

Practical guidance:

• Reading it, studying from it, and keeping notes in your own words is fine.
• Quoting a short passage with attribution is fine.
• Republishing whole chapters, translating the entire thing, or pasting large sections into a company wiki is not clearly fine, and the author has not invited that.
• If you want to build internal training material on top of it, write your own notes instead of copying structure verbatim.

For most people the practical answer is to read it, absorb the framing, and paraphrase. But it costs nothing to know the boundary exists.

How to get the most out of it

Treat these notes as a map and the book as the territory. Read a chapter, then read the matching notes to see what stuck and what did not. Then actually say your design out loud, on a whiteboard or on paper, because system design is a verbal skill. Reading about a caching layer teaches you almost nothing about explaining why you chose it over a read replica when someone is watching.

If you want practice problems after the reading part, these notes will not supply them. Pair them with a separate problem set rather than expecting the notes to cover the applied half.

Source and Accuracy Notes

• Project page: https://github.com/liquidslr/system-design-notes
• Source repository: liquidslr/system-design-notes (verified via GitHub API full_name)
• License: none declared (verified via GitHub API license.spdx_id, returned null)
• Stars at time of writing: 24,674
• Notes rendered at: https://pagefy-blush.vercel.app/system-design/system-design-interview-by-alex-xu