Read less. Run it instead.
The primer is one of the best pieces of writing on system design, and it is a 40,000-word README. This is the same material as a site you can navigate: a simulator that makes the trade-offs behave, the reference split into sections you can link to, and the design problems as exercises you work rather than read.
You are given traffic, a broken topology, an objective and a budget. Buy parts, run the traffic, and find out which node pinned at capacity. The lesson is in the failure, not the diagram.
Every section gets its own page and its own URL, with a summary written for this site on top and the primer’s full text below it. Two sections carry calculators: availability composition, and the latency ladder.
start with the load balancer →The primer’s design problems, each with its constraints and the four-step method as progressive reveals. Step one is open; the rest stay shut so you can attempt it before reading the answer.
work through Pastebin →Section bodies are the primer’s own markdown, fetched from donnemartin/system-design-primer and rebuilt from source, so this site cannot drift from the repo it credits. Summaries, simulations and calculators are written for this site and are marked as such on every page. Content is CC BY 4.0.
20 sections and 7 exercises synced from master on 2026-08-16.