ByteByteGo's 400 diagram-first explainers
System Design 101 collects 400 short guides on how software systems are put together: protocols, APIs, databases, caching, security, deployment, and the architecture of large platforms. Each guide starts from a diagram and walks through it in a few paragraphs. On GitHub the README is a table of contents, and every entry links to the guide's page on bytebytego.com, which opens without an account.
Fifteen sections, 32 company case studies
- Diagram first, little text: three quarters of the guides use fewer than 250 words around their diagram.
- Uneven sections: APIs and web development (50 guides), cloud and distributed systems (49), databases and storage (47), security (35). Payments, DevOps and computer fundamentals (DNS, the OSI model, processes and threads) get their own too.
- Systems in production: Discord moving message storage from MongoDB to Cassandra and then ScyllaDB, Figma scaling Postgres, Netflix's tech stack, the path a Slack message takes.
- Related concepts side by side: proxy vs reverse proxy, load balancer vs API gateway, SOAP vs REST vs GraphQL vs RPC, sessions, cookies, JWT and OAuth 2.0.
- Plain Markdown in the repo: one file per guide under
data/guides/, with title, sections and tags in the front matter. Agrepover a clone searches all 400.
Interview prep and quick protocol lookups
- Getting ready for a system design interview with "How to Ace System Design Interviews" and the reading list in the Technical Interviews section.
- Checking on one diagram what separates HTTP/1, HTTP/2 and HTTP/3, or polling from webhooks.
- Reading how Discord, Airbnb or Uber reworked their architecture before making a similar call.
No commercial reuse, no commits since April 2025
The CC BY-NC-ND 4.0 license rules out commercial use and modified versions. LICENSE.md applies it to all the content. A guide can be shared as is, credited to ByteByteGo. A reworked diagram or a slide in a paid course falls outside what it allows.
The diagrams are not in the repository. The Markdown files point to images hosted on assets.bytebytego.com, so a clone holds the text and nothing else. For a mistake in a diagram, the contribution guide asks for an issue: the team fixes its own source files and republishes.
Everything is in English, and no translation is planned. CONTRIBUTING.md puts it plainly: "We are not planning to translate the guides into other languages at this time." Spanish (#57) and Brazilian Portuguese (#71) translation pull requests opened in late 2023 are still waiting.
The stated audience is interview candidates first. The repository description promises help with system design interviews, and the README also addresses readers who want to understand "how systems work beneath the surface". Yet the Technical Interviews section holds only 5 guides: ByteByteGo sells step-by-step interview prep as separate courses, and every guide page has a button to that catalog.
No release, and no commit since April 4, 2025. Both 2025 commits landed that month. PR #106 removed the long README and its 70 images, replacing them with the site's 400 guides under data/ and a script-generated table of contents; the next commit added the contribution guide. 47 issues and 23 pull requests are open. The repository is not archived, and the site also lists 400 guides.