Introduction Logistics tracking systems process millions of scan events daily, maintain accurate package state, and surface real-time location to customers. […]

Multiplayer game servers synchronize game state across all players in a session with minimal latency. The design must handle packet

IoT platforms ingest telemetry from millions of devices with high write throughput, store time-series data efficiently, and enable real-time alerting

A trading engine matches buy and sell orders for financial instruments. Correctness and latency are paramount — microsecond-level matching with

Airport management systems orchestrate hundreds of daily flight operations including gate assignment, ground handling, baggage routing, and passenger information display.

ATM networks process card transactions across millions of terminals through authorization switches. The design must be highly available, idempotent, and

Introduction KYC (Know Your Customer) requires verifying user identity using government-issued documents. It is a regulatory requirement for fintech companies,

Introduction Collaborative editors in the style of Google Docs allow multiple users to edit the same document simultaneously with real-time

Introduction Live streaming requires low-latency ingest, real-time transcoding to multiple bitrates, and global CDN distribution to millions of concurrent viewers.

Real-time traffic routing is one of the canonical systems design problems — and also one of the most algorithm-heavy LLD

Autonomous vehicle fleet management sits at the intersection of real-time embedded systems, cloud infrastructure, and safety-critical engineering. This LLD covers

Drone delivery is one of the more mechanically complex LLD problems: you have a physical object moving through three-dimensional space,

An ad serving system delivers targeted advertisements to users in real time, managing the full lifecycle from auction to billing.

A sports betting platform is one of the harder LLD problems because it combines real-time odds management, strict financial controls,

A customer support ticket system coordinates incoming requests across channels, routes them to the right agents, enforces SLAs, and provides