⏱ 6 min read User Session Management — Low-Level Design A session management system authenticates users and maintains their login state across requests. It […] Read article

⏱ 6 min read Geo Search System — Low-Level Design A geo search system finds nearby entities (restaurants, drivers, listings) given a user’s location. Read article

⏱ 6 min read Currency Converter Service — Low-Level Design A currency converter service fetches exchange rates from external providers, caches them, and applies Read article

⏱ 7 min read Tagging System — Low-Level Design A tagging system allows attaching labels to content for categorization, filtering, and discovery. It must Read article

⏱ 7 min read Like System — Low-Level Design A like system records user reactions to content and displays counts. At scale, naive approaches Read article

⏱ 7 min read Comments System — Low-Level Design A comments system supports threaded discussion on content: flat comments, nested replies, sorting, pagination, and Read article

⏱ 6 min read Email Queue System — Low-Level Design An email queue system buffers outgoing emails from application code, delivers them reliably through Read article

⏱ 6 min read Waitlist System — Low-Level Design A waitlist system queues users for access to a limited resource: early access to a Read article

⏱ 6 min read Booking System — Low-Level Design A booking system manages reservations for time-slotted resources: hotel rooms, restaurant tables, meeting rooms, or Read article

⏱ 5 min read Dark Mode System — Low-Level Design A dark mode system persists a user’s theme preference, propagates it across devices, and Read article

⏱ 6 min read Payment Split System — Low-Level Design A payment split system divides a single transaction among multiple parties: splitting a restaurant Read article

⏱ 6 min read Archive System — Low-Level Design An archive system moves cold data from primary storage to cheaper, slower tiers while keeping Read article

⏱ 5 min read What is a Product Catalog System? A product catalog stores and serves product data: names, descriptions, images, prices, variants, and Read article

⏱ 5 min read What is a Storage Quota System? A storage quota system tracks and enforces per-user limits on resource consumption: disk storage Read article

⏱ 5 min read What is a Returns Portal? A returns portal allows customers to self-service returns and exchanges: select items to return, choose Read article