System Design
Scale, latency, durability
Real-world distributed systems: scaling, caching, databases, queues, and end-to-end case studies (Twitter feed, URL shortener).
Latency, throughput, availability, durability, and the CAP theorem — the vocabulary you'll use forever.
How systems grow from one box to thousands, and the strategies for splitting state across them.
The single highest-leverage tool in performance work — and the easiest place to introduce subtle bugs.
How to pick a database, what an index actually is, and why replication is non-negotiable.
How decoupled services talk to each other without falling over — message queues, event streams, and pub/sub.
End-to-end walkthrough of the most-asked system design interview question.
The smallest interesting system design problem — and a great showcase of read-heavy optimization.