Qianji
The Mechanics Behind 10M QPS, All in One Library
Qianji is an offline-first knowledge base app for high-concurrency system architecture. 240 hands-on articles trace the evolution from 100K to 10M QPS across seven domains — network architecture, load balancing, caching, databases, message queues, service architecture, and monitoring & operations — with new content added continuously. Dual navigation via table of contents and architecture diagram turns linear articles into a connected web of knowledge.
Why Qianji
First principles to explain the mechanics, production post-mortems to distill the trade-offs — a coherent system, not scattered fragments.
Dual Navigation: A Table of Contents Plus an Architecture Diagram
A one-of-a-kind architecture-diagram view: seven nodes map to the seven domains, and tapping any node jumps straight to the related articles — follow the request lifecycle and see the key trade-off at every hop.
240 Hands-On Articles on Architecture Evolution
Spanning 7 domains and 49 subcategories, the articles build layer by layer along the 100K-to-10M QPS storyline, pairing rich architecture diagrams with real production post-mortems — and the library keeps growing.
Native Reader with Offline Full-Text Search
Native Markdown rendering with syntax-highlighted code, tables, and zoomable images; full-text search works fully offline with every hit highlighted, and dark mode keeps late-night reading easy on the eyes.
Everything Built In, No Network Needed
Articles and diagrams ship inside the install package, so you can read on the subway, on an international flight, or in a server room with no signal — with no account, no ads, and no analytics or tracking.
Highlights, Notes, and Bookmarks
Highlight key takeaways as you read, jot down annotations, and bookmark the articles you reach for most; a single hub gathers all your notes for review, and reading progress is tracked automatically.
Single-Article Image Export & Sharing (Coming Soon)
Export any single article as a cover image in one tap, with a mobile-friendly layout and a wider desktop layout. To protect the content, export and sharing are limited to individual articles; PDF and bulk export are not available.
How to Use Qianji
From install to mastery in three steps.
Install from the Store and Start Reading
Download it from your app store and start reading right away — all content ships inside the package, with no sign-up and no network required.
Enter Through Either Navigation
Read the seven domains in order from the table of contents, or switch to the architecture-diagram view and tap the node you're wrestling with right now — start where the problem lives.
Read Deep, Annotate, Search Offline Anytime
Highlight and take notes as you read, and bookmark the key articles; when a problem comes up, offline full-text search finds the answer fast, so key takeaways are always close at hand.
Product Screenshots
Who Uses Qianji
Four roles, one library.
Quick Answers on the High-Concurrency Front Line
When a backend engineer hits a tough trade-off in rate limiting, cache consistency, or database sharding, offline search jumps straight to the right article — highlight and bookmark it, and it's back in seconds next time.
A Reference for Architecture Evolution Decisions
When drafting a design, open the architecture-diagram view and walk the request lifecycle hop by hop to examine the reasoning behind each trade-off, giving team reviews a clear and traceable architectural foundation.
Big-Tech Interview Sprint
Read offline on your commute and grasp the principles behind stock interview questions as one coherent system; with notes and highlights, run a full systematic review before the interview.
A Structured Intro to Large-Scale Architecture
Read the seven domains in order, build a big-picture mental model with the architecture diagram, and let related-article recommendations tie scattered concepts into a single web.
Download Qianji
The Android installer is now available from the official website and will also roll out to Android app stores. iOS and HarmonyOS will follow.
Android is a trademark of Google LLC.
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Send Us Your Corrections and Suggestions
Qianji and the library it houses are both evolving. Whether it's a correction to an article, a topic you'd like covered, a feature request, or a bug report, write to us — we read every message carefully.