Understand how something works
Read a guide
Illustrated, end-to-end walkthroughs of the systems under the web.
Semicolony is a study site for how real systems work — guides, interactive simulators, roadmaps, deep dives, and a reference library. Pick the door that fits.
Illustrated, end-to-end walkthroughs of the systems under the web.
Hand-built, interactive models you can step through and break.
Structured routes through a discipline, each topic linked to a deep dive.
Single-page deep dives across distributed systems, databases, networking, and more.
Time-boxed flows: a system-design simulator, flashcards, and coding patterns.
Data structures, foundations, annotated papers, the people behind the ideas.
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