Author name: techinterview.org

⏱ 8 min read A sports betting platform is one of the harder LLD problems because it combines real-time odds management, strict financial controls, […] Read article

⏱ 7 min read Airline reservation systems are among the most demanding transactional workloads: thousands of concurrent seat holds, strict inventory partitioning by fare Read article

⏱ 7 min read A library management system handles catalog browsing, checkouts, returns, reservations, and fines. This low level design covers the core schemas Read article

⏱ 6 min read A device fingerprinting service identifies and tracks devices across sessions without relying on cookies or stored identifiers. It is a Read article

⏱ 6 min read A QR code generation service must handle encoding, error correction, output formats, and at scale — bulk generation for campaigns, Read article

⏱ 6 min read A barcode scanner service must handle multiple symbologies, noisy real-world images, fast mobile frame processing, and integration with product catalogs. Read article

⏱ 6 min read An OCR service must handle raw document images, extract structured text, assess confidence, and process jobs asynchronously at scale. Here Read article

⏱ 5 min read Autocorrect differs from a spell checker in intent: rather than flagging errors for the user to fix, it silently replaces Read article

⏱ 8 min read In a SaaS product, onboarding a new customer involves far more than creating a database row. The tenant provisioning service Read article

⏱ 8 min read Configuration drift is one of the most common root causes of production incidents. A config diff and change management service Read article

⏱ 7 min read API key rotation is a security control that limits the blast radius of a leaked credential. A well-designed rotation service Read article

⏱ 7 min read Experiment Logging and Analysis Service An experiment logging and analysis service captures assignment and metric events from running A/B tests, Read article

⏱ 7 min read Real-Time Location Service A real-time location service ingests high-frequency position updates from mobile clients, indexes them for low-latency spatial queries, Read article

⏱ 6 min read Low Level Design: Pastebin Service A Pastebin service lets users store and share text (code, configs, logs) via a short Read article

⏱ 4 min read Ingestion: Chunked Upload and Raw Storage Large video files cannot be uploaded in a single HTTP request reliably. The ingestion Read article