Alex Xu's System Design Interview: An Insider’s Guide is a highly-regarded resource for mastering the technical architecture interviews common at major tech companies. The book is primarily divided into two volumes, each serving as a comprehensive manual for building scalable, distributed systems. Core Framework for Interviews
If you search for the "top" PDF, you want the edition that includes modern challenges like WebSocket connections and Quorum consensus—which Volume 2 covers extensively.
If you have browsed through any tech interview preparation forum in the last five years, you have seen it: the orange book. Alex Wu’s System Design Interview – An Insider’s Guide (Volumes 1 and 2) has become the de facto standard for cracking the infamous system design round at FAANG and Tier-1 companies.
Alex Xu popularized a structured approach to prevent candidates from getting lost in the "open-ended" nature of these interviews: