StackScholar

Interactive Toolkit

Every simulator from the course in one place - 17 calculators and live models. Some of this material genuinely cannot be learned from prose: you have to break a server and watch where the traffic goes.

Estimation and capacity

The arithmetic that turns a vague brief into a concrete architecture. Reach an order of magnitude, then use it to rule designs out.

Databases and storage

Index mechanics, concurrency anomalies and probabilistic structures - the concepts that are far easier to see than to read about.

Scaling and distribution

Where requests go, how keys map to nodes, and what happens when a node dies.

Caching, traffic and flow control

The components that stand between your users and your database, and the failure modes that make them interesting.

These make more sense with the lesson around them

Each tool sits inside a lesson that explains what you are looking at and why it matters in an interview. 38 lessons, 71 questions, all free.

Browse the curriculum