System Design 101

What it contains

System Design 101 started as a GitHub repository of diagrams with brief notes. The README now works as a table of contents linking to the same guides on the ByteByteGo website, where they are free to read. As of September 2026 it lists about 400 guides in fifteen categories:

• API and web development (REST, GraphQL, gRPC, WebSocket, HTTP versions, API gateways)
• Real-world case studies
• AI and machine learning
• Database and storage
• Caching and performance
• Payment and fintech
• Software architecture and software development
• Cloud and distributed systems
• DevOps and CI/CD
• Security
• DevTools and productivity
• Computer fundamentals and "How it works?" explainers
• Technical interviews

Typical titles include "Reverse Proxy vs. API Gateway vs. Load Balancer", "What makes HTTP2 faster than HTTP1?" and "SOAP vs REST vs GraphQL vs RPC".

The numbers

The repository has about 90k GitHub stars and 10k forks as of September 2026. Its last commit was in April 2025, when content moved to the website. The content is licensed CC BY-NC-ND 4.0, so you can share it with attribution but not modify it or use it commercially.

Why the one-diagram format works

There is a difference between learning a concept and recalling it later. Once you understand how a reverse proxy differs from a load balancer, what you need months later is a thirty-second reminder, not another long article. Each guide is designed for that job: one picture, a few annotations, done.

How to use it

• As revision: skim a category the week before a design discussion or interview.
• As a lookup: when a colleague mentions a protocol or pattern you half-know, search the guide list first.
• Test yourself: read the title, try to sketch the diagram from memory, then compare.
• Do not use it as a first course. A diagram compresses a lot. If a guide shows something you have never learned, go and learn it properly from a book or course, then come back.

Where it falls short

The format leaves out trade-offs, failure behaviour and the "why" behind choices, which are exactly what deeper questions probe. Some diagrams simplify to the point of being slightly misleading. And because the repository is no longer the main home, the newest guides live on the website rather than GitHub.

Common questions

Is it free? Yes. The guides are free on the website and indexed on GitHub. The paid ByteByteGo courses are separate.

Is it the same as the newsletter? Many guides first appeared in the ByteByteGo newsletter. This is the organised, searchable archive.

Can I use the diagrams in my own slides? Only with attribution and for non-commercial use, and without modification, under the CC BY-NC-ND licence.

Best for: engineers and students who want quick visual refreshers on system design and web concepts.