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Status: OperationalVersion: 4.2.0
System Design
OverviewTheory lessonsHLDLLD
All SeriesSeries
Distributed Systems
All System Design modules

Module 4 · Complex Systems

High-Level Design (HLD) Real-World Case Studies

End-to-end planetary-scale architectural case studies derived from first principles with back-of-the-envelope capacity estimation, data schemas, API contracts, and failure mitigations.

10 lessons available·365 minutes·6 coming soon
Start module

Lesson plan

What you will learn

01Scalable URL Shortener (TinyURL & Bitly)Design a high-throughput URL shortening service handling 100M new URLs/month with Base62 encoding, collision-aware ID generation, 100:1 read-to-write caching, and explicit redirect cache policy. 30 min02Planetary Distributed Rate Limiter (Cloudflare & Stripe)Architect a planetary rate limiting engine processing 1M+ req/s with multi-tier enforcement, Redis Lua sliding window counters, local memory fallbacks, and multi-region synchronization. 35 min03Pastebin & Ephemeral Blob StorageDesign a paste service for 50M creates/day using scoped direct uploads, separate metadata and blob storage, logical expiry, lifecycle cleanup, and safe caching. 40 min04Social Timeline & Newsfeed (Twitter/X & Meta Feed)Architect a planetary newsfeed supporting 500M DAU: Fanout-on-Write (push for normal users) vs Fanout-on-Read (pull for celebrities), hybrid fanout engines, and Redis timeline lists. 35 min05Global Real-Time Chat & Messaging (Discord & WhatsApp)Build a planetary messaging system using a 50M-concurrent-connection worked example with persistent WebSocket gateways, scoped ordering, distributed presence, durable logs, and delivery receipts. 35 min06High-Throughput Video Streaming & Ingestion (Netflix & YouTube)Design a planetary video streaming architecture: distributed chunking and transcoding ladders (VMAF), Adaptive Bitrate Streaming (HLS/DASH), Open Connect Appliance CDN pre-positioning, and metadata sharding. 35 min07Ride-Sharing Proximity Dispatch (Uber & Lyft)Architect a ride-sharing proximity system using a 1M-active-driver and 10M-rides/day worked example: location ingestion, H3 candidate search, in-memory geospatial state, and dispatch. 35 min08Distributed Key-Value Store (Amazon Dynamo & Cassandra)Build a Dynamo-style key-value store while separating quorum intersection from database guarantees, then trace hints, read repair, anti-entropy, tombstones, and recovery load. 45 min09Flash Sale & High-Concurrency Inventory ReservationDesign an e-commerce flash sale system handling 500k QPS surges: multi-tier traffic shedding, Redis Lua atomic stock decrement, inventory sharding across keys, async order creation queues, and anti-overselling DB constraints. 35 min10Distributed Search Autocomplete & Typeahead EngineDesign a low-latency typeahead service with bounded prefix lookup, versioned immutable indexes, safe ranking, debouncing, cancellation, and atomic rollout. 40 min
Coming next in this module
  • Distributed Job Scheduler & Workflow Engine (Temporal & Airflow)
  • Large-Scale Distributed Web Crawler (Googlebot)
  • Time-Series Metrics & Alerting Monitoring (Prometheus & Gorilla)
  • Distributed Payment Gateway & Immutable Financial Ledger
  • Real-Time Collaborative Document Editor (CRDTs & OT)
  • Ad Click Event Aggregator & Real-Time Stream Analytics

Module outcome

Confidently design flagship systems in 45-minute FAANG interviews, deriving components from concrete mathematical constraints and answering complex examiner deep dives.

Prerequisite

Module 1 (Foundations), Module 2 (Core Infrastructure), and Module 3 (Distributed Mechanics).

Mental model

Start simple, measure hardware and network bounds, identify the first bottleneck, and introduce components only when mathematical evidence demands them.

Module challenge

Planetary Architecture Portfolio

Deliver complete, production-grade architectural blueprints for three distinct domains: a real-time messaging platform (Discord), a geospatial dispatch engine (Uber), and an e-commerce flash sale system (Amazon).

  • Complete back-of-the-envelope capacity sheets with peak QPS, bandwidth, 5-year storage, and RAM sizing.
  • Production data models with primary keys, partition keys, and secondary index strategies.
  • Detailed failure recovery walkthrough for cross-region partition and primary node crash scenarios.

Course baseline

System Design 2026.1

Reviewed 2026-09-14

Previous module Distributed Systems Mechanics & ReliabilityNext moduleLow-Level Design (LLD) Theory: OOP, SOLID & Design Patterns