⏱ 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

⏱ 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

⏱ 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

⏱ 6 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

⏱ 6 min read Requirements and Core Challenge Functional: multiple users edit the same document simultaneously, changes from all users are reflected in real Read article

⏱ 11 min read Problem Statement Design a content moderation system for a social platform. User-generated content (text, images, video) must be screened before Read article

⏱ 8 min read Scope and Requirements A payment processing platform handles money movement between buyers and sellers through external payment processors (Stripe, Adyen, Read article