System Design Notebook

System Design Notebook is a structured, personal knowledge base for learning and practicing system design, written in a way that mirrors real interview and on-the-job thinking. Instead of being a single long article, it’s split into topics like scalability, load balancing, data partitioning, caching, availability, consistency, and communication patterns, so you can study them in isolation. It emphasizes reasoning: why you pick a certain database, why you shard, why you put a queue, and what trade-offs come with each choice. The notes often connect abstract concepts to concrete systems such as social networks, feeds, chat, and file storage, which makes it easier to translate theory into design diagrams. It is meant to be expanded over time, so you can treat it as a living notebook you keep coming back to before interviews or architecture reviews. The repo is especially helpful for people who already know the basics of backend but want to articulate system design decisions clearly.