System Design Handbook

Curated practical notes for backend engineers. This repo collects concise explanations, checklists, and PDFs on Networking, Distributed Systems, Java internals, Low-Level Design patterns, LeetCode utilities, and real-world estimations. Use it to prepare for interviews, design reviews, and to build reliable systems.

What you’ll find

• Networking fundamentals and HTTP status references
• Distributed systems patterns: CAP, consistent hashing, caching, load balancing
• URL shortener design walkthrough with estimations and PDF references
• Java internals: JVM, memory, JIT, slowness causes
• LLD patterns with examples (Factory, Strategy, Adapter, Observer, Proxy, etc.)
• Utilities and scripts for coding interviews

Quick start

Open the folders in this order for a learning path:

1. Fundamentals → Networking → HTTP
2. Distributed Systems → Intro → Caching → URL Shortener
3. Low Level Design → Creational/Behavioral/Structural patterns
4. Java internals
5. LeetCode utilities and cheat sheets

Contributing

PRs welcome. Add clear explanations, diagrams, and runnable examples. Keep files small and focused.