Category
high level design
19 articles
System Design HLD Example: Web Crawler
TLDR: A distributed web crawler needs three things to work at scale: a priority-aware URL Frontier that drives crawl order, a Politeness Module that enforces per-domain rate limits so crawlers don't take down small sites, and a two-layer deduplicatio...
System Design HLD Example: Video Streaming (YouTube/Netflix)
TLDR: A video streaming platform is two separate systems stitched together — a batch-oriented transcoding pipeline that converts raw uploads into multi-resolution HLS/DASH segments, and a real-time delivery network of CDN edge nodes that serve those ...
System Design HLD Example: Ride Sharing (Uber)
TLDR: A ride-sharing platform is a real-time geospatial matching system. Drivers push GPS location every 5 seconds into a Redis geospatial index. When a rider requests a trip, the Matching Service runs a GEORADIUS query to find nearby available drive...
System Design HLD Example: Proximity Service (Yelp)
TLDR: A proximity service (Yelp/Google Places) encodes every business location into a geohash string, indexes it in a B-tree column, and queries the center cell plus its 8 neighbors to guarantee no boundary misses. Redis GEORADIUS caches hot-cell res...
System Design HLD Example: Real-Time Leaderboard
TLDR: Real-time leaderboards for 10M+ players require Redis Sorted Sets as the primary ranking index — ZADD updates a player's score in O(log N) and ZREVRANK returns their global rank in O(log N), keeping rank queries under 10ms at any scale. SQL ORD...
System Design HLD Example: Distributed Job Scheduler
TLDR: Design a distributed job scheduler for one-time and recurring (cron) jobs at scale. This article covers the full solution: job definition storage with next_fire_time indexing, Redis sorted set for sub-millisecond trigger lookup, optimistic lock...
System Design HLD Example: Hotel Booking System (Airbnb)
TLDR: Design a hotel booking system like Airbnb. This article covers availability tracking with date-level inventory, double-booking prevention via optimistic locking, two-phase reservation (hold → confirm), geospatial search with Elasticsearch, and ...
System Design HLD Example: E-Commerce Platform (Amazon)
TLDR: A large-scale e-commerce platform separates catalog, cart, inventory, orders, and payments into independent services. The hardest unsolved problem in every interview is inventory correctness under concurrent checkout — solved with Redis atomic ...
System Design HLD Example: Collaborative Document Editing (Google Docs)
TLDR: Real-time collaborative document editing uses Operational Transformation (OT) or CRDTs to ensure all clients converge to the same document state regardless of concurrent edit ordering. The key insight: every operation must be transformed agains...
System Design HLD Example: URL Shortener (TinyURL and Bitly)
TLDR: Design a URL shortener like TinyURL or Bitly. This article now follows your system design interview template flow: use cases, requirements, estimations, design goals, HLD, and design deep dive. TLDR: A URL shortener converts long links into com...
System Design HLD Example: Search Autocomplete
TLDR: Design search autocomplete for a large-scale product. This article follows the system design interview template flow: use cases, requirements, estimations, design goals, HLD, and design deep dive. TLDR: Sub-10ms prefix lookups via Redis sorted ...
System Design HLD Example: Rate Limiter (Global API Protection)
TLDR: Design a distributed rate limiter for public APIs. This article covers the full solution: per-user/per-key policies, endpoint quotas, burst handling with token bucket, atomic Redis Lua enforcement, and retry metadata. TLDR: A distributed rate l...
System Design HLD Example: Payment Processing Platform
TLDR: Design a payment processing system for online checkout. This article covers idempotent authorization, two-phase authorize-capture, double-entry ledger writes, webhook delivery with retry, and nightly reconciliation — with concrete schema, Redis...
System Design HLD Example: Notification Service (Email, SMS, Push)
TLDR: Design a notification service for email, SMS, and push channels. This article covers the full solution: data model, per-channel queue isolation, deduplication, retry with dead-letter queue, provider failover, and delivery tracking. TLDR: A noti...
System Design HLD Example: News Feed (Home Timeline)
TLDR: Design a news feed for a social platform. This article now follows your system design interview template flow: use cases, requirements, estimations, design goals, HLD, and design deep dive. TLDR: A news feed system builds personalized timelines...
System Design HLD Example: File Storage and Sync (Google Drive and Dropbox)
TLDR: Design a cloud file storage and sync system like Dropbox. This article now follows your system design interview template flow: use cases, requirements, estimations, design goals, HLD, and design deep dive. TLDR: File storage and sync systems se...
System Design HLD Example: Distributed Cache Platform
TLDR: A distributed cache reduces read latency and source-of-truth load while introducing consistency trade-offs. This walkthrough solves the full problem: consistent hashing for online scaling, per-namespace eviction policies, synchronous invalidati...
System Design HLD Example: Chat and Messaging Platform
TLDR: Design a chat application like WhatsApp or Slack direct messages. This article covers the full solution: data model, per-feature deep dives, WebSocket fan-out, delivery receipts, presence, reconnect sync, and multi-device behavior. TLDR: A chat...
System Design HLD Example: API Gateway for Microservices
TLDR: Design an API gateway for a microservice platform. This article now follows your system design interview template flow: use cases, requirements, estimations, design goals, HLD, and design deep dive. TLDR: An API gateway centralizes ingress conc...