High-Level Design
System Design › High-Level DesignDesign a Notification System — System Design Interview
Design a multi-channel notification system (push, SMS, email) at scale: the queue-based async architecture, per-channel workers, third-party providers, retries and dead-letter queues, dedupe, rate limiting, and priority.
System Design › High-Level DesignDesign a Chat System (WhatsApp / Messenger) — System Design
Design a real-time chat system end to end: WebSockets, the connection-routing problem (which server holds a user's socket), store-and-forward for reliability and offline delivery, group fan-out, and presence.
System Design › High-Level DesignDesign a News Feed (Facebook / Twitter) — System Design
Design a social news feed end to end: the fan-out problem (push vs pull), the celebrity fan-out storm, the hybrid solution, async fan-out workers, feed caching, and modern ranking.
System Design › High-Level DesignDesign a Rate Limiter — System Design Interview
Design a distributed rate limiter end to end: where it lives (the API gateway), which algorithm, and the core challenge — sharing counters across many servers with Redis and atomic increments.
System Design › High-Level DesignDesign a URL Shortener (TinyURL / bit.ly) — System Design
The classic system design warm-up, solved end to end: requirements, scale estimation, Base62 short codes, generating unique codes without collisions, the data model, caching the redirects, and scaling.