System Design

⏱ 7 min read Requirements Functional requirements for a URL shortener: Create a short URL from a long original URL Redirect users from the […] Read article

⏱ 9 min read Payment State Machine A payment must move through well-defined states. Never allow arbitrary transitions or skipped states. INITIATED -> PROCESSING Read article

⏱ 12 min read Caching is the single highest-leverage optimization in most systems. A well-designed cache can cut database load by 90% and reduce Read article

⏱ 9 min read Search autocomplete is one of the most latency-sensitive features in any product. Users expect suggestions within 100ms of each keystroke. Read article

⏱ 8 min read Rate limiting is a core system design topic. This guide covers every major algorithm, their trade-offs, and Redis implementation patterns Read article

⏱ 11 min read Authentication is one of the most common low-level design questions in system design interviews, and one of the most commonly Read article

⏱ 9 min read Core Models: ACL, RBAC, ABAC, ReBAC Access control models define how permissions are assigned and evaluated. Each has different tradeoffs Read article

⏱ 4 min read System Design: A/B Testing Platform An A/B testing platform lets product teams run controlled experiments – assigning users to variants, Read article

⏱ 5 min read Low-Level Design: Workflow Engine A workflow engine executes directed acyclic graphs (DAGs) of steps, handling parallelism, retries, and failure propagation. Read article

⏱ 4 min read Core Entities Diff Computation Server-side diff using the Myers diff algorithm (also used by git). Output stored as unified diff Read article

⏱ 5 min read Core Entities License Management Unlike physical books, digital copies can support multiple simultaneous loans up to a licensed limit. The Read article

⏱ 7 min read Core Entities and Schema The recommendation engine centers on four entities. User: user_id, preferences JSONB, created_at. Item: item_id, category, features Read article

⏱ 9 min read Core Entities Two primary entities drive the design: Token Bucket Algorithm Tokens refill at rate r tokens/second up to capacity Read article

⏱ 5 min read Core Entities and Fan-Out Strategies Post: post_id, author_id, content, media_urls (array), created_at, like_count, comment_count, share_count. Follow: follower_id, followee_id, created_at. FeedItem: Read article

⏱ 5 min read Requirements and Scale Functional: turn-by-turn navigation, ETA estimation, real-time traffic updates, points of interest search, route alternatives. Non-functional: 1B daily Read article