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System Design HLD Example: URL Shortener (TinyURL and Bitly)

3d ago · 22 min read · 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: Notification Service (Email, SMS, Push)

3d ago · 24 min read · 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: Search Autocomplete

3d ago · 26 min read · 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)

3d ago · 27 min read · 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

3d ago · 24 min read · 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: News Feed (Home Timeline)

3d ago · 21 min read · 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)

3d ago · 24 min read · 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

3d ago · 27 min read · 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

3d ago · 24 min read · 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

3d ago · 25 min read · 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...