Popular System Design Examples Articles

This case study explains how to design a high-scale lead lookup system for 200M users, where the main requirement is fast lookup by phone number, email address, or SSN while still supporting contact reassignment and full contact history.

A file storage service allows users to upload, download, organize, and synchronize files across devices. At small scale, files can be written directly to a server's local disk. At large scale, that approach breaks down because application servers are ephemeral, files can be gigabytes in size, storag

A chat application looks simple from the client perspective: a user sends a message and another user receives it. At scale, that interaction requires persistent connections, message routing, durable storage, ordering, offline delivery, synchronization across multiple devices, and infrastructure capa

A notification system delivers messages to users through channels such as mobile push, email, and SMS. Sending one notification is straightforward. Sending millions reliably becomes a distributed-systems problem involving asynchronous processing, fan-out, user preferences, provider rate limits, retr

This case study describes a production blog platform backed entirely by Amazon DynamoDB . The system serves typical blog workloads such as “latest posts”, “most popular posts”, “posts by author”, and “posts by tag”, while also supporting administrative queries like user moderation and contact messag

A URL shortener converts a long URL into a compact identifier that redirects users to the original destination. The product appears simple, but designing it at large scale introduces important system design questions around identifier generation, storage, caching, database partitioning, redirects, a

This case study explains how a simple user-owned SaaS application was migrated to a multi-tenant architecture that supports organizations, teams, shared resource ownership, tenant isolation, and role-based permissions.