System Design, From First Principles

A first-principles guide to designing real systems. We build understanding in dependency order — each topic only uses ideas already covered. For every decision, keep asking one question: what does this buy us, and what does it cost? Every architecture choice is a trade-off; this book is about seeing both sides. Read in order, and after each page answer the Check your understanding questions in your own words. Depth over speed.

Part 0 · Foundations — Why Systems Are Hard

Part 1 · Core Building Blocks

Part 2 · Data: Storage & Retrieval

Part 3 · Scaling & Performance

Part 4 · Distributed Systems Theory

Part 5 · Communication & APIs

Part 6 · Reliability & Resilience

Part 7 · Observability & Operations

Part 8 · Security & Trust Boundaries

Part 9 · Case Studies — Designing Real Systems

The “design X” track — full walkthroughs with the reasoning and trade-offs at every step.

Part 10 · Advanced & Rare Concepts

The senior-level track — the subtle mechanics and failure modes most engineers learn the hard way.