System Design

What Are Feature Flags? Feature flags (also called feature toggles or feature gates) decouple code deployment from feature release. A […]

Why Distributed Locks Are Needed In a distributed system, multiple instances of a service may run concurrently. When these instances

What Makes Stock Exchanges Hard to Design A stock exchange is one of the most demanding distributed systems: it must

Why Content Moderation Is a Hard Systems Problem A platform with 500 million daily active users generates billions of pieces

Analytics vs Transactional Systems OLTP (Online Transaction Processing) systems like PostgreSQL are optimized for short, frequent reads and writes to

What Is an API Gateway? An API gateway is the single entry point for all client requests to a microservices

Why Recommendations Matter Netflix reports that 80% of content watched is discovered through recommendations. Spotify generates 30% of its streams

Problem Overview Design a hotel or short-term rental booking system like Airbnb or Booking.com. Users search for available properties in

Why Payment Systems Are Hard Payment systems are among the hardest distributed systems to design because money movement requires exactly-once

Problem Overview Design a location-based service that allows users to find nearby businesses (Yelp) or navigate between locations (Google Maps).

Problem Overview Design a file storage and sync service like Dropbox or Google Drive. Users can upload files up to

What Is a Web Crawler? A web crawler (spider) systematically browses the web, downloading pages and extracting links to discover

What Is a CDN? A Content Delivery Network is a globally distributed network of servers (Points of Presence, or PoPs)

The Core Challenge Real-time collaborative editing requires multiple users to edit the same document simultaneously and see each other changes

What Is a Typeahead System? A typeahead (search autocomplete) system returns a ranked list of query completions as the user