A group chat: one register, many sockets

The socket lives on one server, a directory says which. The group stores each message once, each member keeps a cursor, and a retry carries the same client…

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  • 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.
  • System Design — Eight interview case studies, from a flash sale and Tatkal to a live final and a chat model, plus JWT in separate chapters.
  • 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.
  • 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 — HTML labs first, then a full pass of WAI-ARIA 1.3: naming, every state, widget and structure roles, live regions, ariaNotify, and relationships.
  • 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.