Start here in System Design
How the interview is graded at each level, the five-phase route through any question, and the numbers that tell you when one box is enough.
Related chapters
- How a system design interview is graded
- The delivery framework: five phases and a clock
- Numbers to know: what one machine can really do
- System Design Concepts: CAP, SQL vs NoSQL, Message Queues
- SQL vs NoSQL: How to Choose a Database (System Design)
- CAP Theorem Explained Simply, with Examples
- Why Use a Message Queue? System Design Explained
- Message Queue vs Pub/Sub vs Kafka: Differences
- System Design Case Studies: Flash Sale, Chat, ChatGPT
- Flash Sale System Design: Who Gets the Last Item
- Food Delivery App System Design: Which Database?
- Cache Stampede: Why the Database Fell Over and the Fix
- Live Streaming System Design: Scaling for a Final
- ChatGPT System Design: Streaming LLM Responses
- RAG System Design: Product Q&A on Sale Day
- IRCTC Tatkal System Design: Booking Under Extreme Load
- Group Chat System Design: WebSockets and Fan-Out
- Authentication in System Design: Sessions, JWT, OAuth
- Authentication Methods Compared: Sessions, JWT, OAuth
- JWT in System Design: Sessions, Revocation, Refresh Tokens
- JWT Interview Questions and Answers
- Life of a session, step by step
- JWT Structure Explained: Header, Payload, Signature
- Forge lab: why verification must be strict
- JWT vs Session Authentication: Which to Use
- The validation pipeline: where a bad request dies
- How to Revoke a JWT: Blocklists and Short Expiry
- Refresh Tokens and Rotation Explained
- Logout in depth: one device, all devices, SSO
- JWT Security Best Practices
- OAuth 2.0 and OpenID Connect Explained
- Where to Store JWT: localStorage vs HttpOnly Cookie
- Microservices, keys, and trust boundaries
- Sender-constrained tokens: making a stolen token useless
- Authentication vs Authorization Middleware
- Failure explorer: what breaks when X fails
- Capacity planner: sessions vs JWT vs hybrid
- Edge cases catalog
- Test it, measure it, migrate to it
- Anti-patterns to reject in a design review
- Design checklist and cheat sheet
Keep learning
More courses
- Jobs, linked to lessons — Browse jobs where every requirement links to the chapter that teaches it. See how ready you are, how long the gap takes to close, and which listings look stale.
- Match a job post to courses — Paste a job post. Each skill is matched to a track here and put in learning order, foundations first.
- React from open source with patterns — Patterns extracted from Material UI, Radix, React Aria, React Hook Form, Redux Toolkit, TanStack, and Next.js — not slides about hooks.
- Database in depth — How a query becomes work. Indexes, isolation, locks, and the plans that explain why a page is slow — not an ORM tour.
- Microservices — Microservice patterns one diagram at a time: how to split a monolith, how services talk, and how data stays consistent without distributed transactions.
- Kafka — A beginner-to-senior path through event logs, reliable delivery, production operations, and disaster recovery.
- Frontend system design — How a UI is sliced when it is a product, not a page: ownership of state, cache, routes, and what happens when the network lies.
- TypeScript in depth — The type system as a design tool. Inference, narrowing, generics, and the errors that mean the model is wrong — not a catalog of utility types.
- CSS in depth — See the box, then the page. Visual chapters from the box model through Flexbox surprises, Grid, selectors, and units, then backgrounds, shapes, and visual effects, each with a playground.
- Accessibility — Foundations first (WCAG in plain words, semantic HTML, lists, alt text), then hands-on HTML labs, a full pass of WAI-ARIA 1.3, and a final fix-the-page challenge.
- Docker — What an image is, why layers cache, and how containers find each other on a network.
- Redis — Fifteen Redis patterns, one picture each: cache, session, lock, counter, rate limiter, queue, and when Redis is the wrong tool.