13. Content Delivery Networks (CDN): Edge Caching, Dynamic Site Acceleration & Origin Shielding • High-Level System Design (HLD): Distributed Systems at Scale • Rishabh Ki Kaksha

High-Level System Design (HLD): Distributed Systems at Scale › 13. Content Delivery Networks (CDN): Edge Caching, Dynamic Site Acceleration & Origin Shielding

40 mins

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Course Syllabus

Module 1: Distributed Systems Core & Scalability Fundamentals

01. Scalability Dimensions: Vertical Scaling vs Horizontal Scaling & Latency vs Throughput 02. CAP Theorem vs PACELC Theorem: Consistency, Availability & Partition Tolerance Tradeoffs 03. Consistency Models: Strong Consistency, Eventual Consistency, Read-Your-Writes & Monotonic Reads

Module 2: Networking, Load Balancing & Reverse Proxies

04. Layer 4 vs Layer 7 Load Balancing: Round Robin, Weighted, Least Connections & IP Hash 05. High-Availability Load Balancers: Keepalived, VRRP, Anycast DNS & Failover Clustering 06. API Gateway Pattern: Authentication, Rate Limiting, Request Routing & Circuit Breakers

Module 3: Database Scaling: Sharding, Replication & Distributed Transactions

07. Database Replication: Master-Slave vs Multi-Master & Synchronous vs Asynchronous Replication 08. Database Sharding: Horizontal Partitioning, Directory-Based Sharding & Rebalancing Hotspots 09. Distributed Transactions: Two-Phase Commit (2PC) vs Saga Pattern (Choreography vs Orchestration)

Module 4: Caching Architectures, CDN & Consistent Hashing

10. Caching Strategies: Cache-Aside, Read-Through, Write-Through, Write-Around & Write-Back 11. Cache Invalidation Nightmares: Cache Avalanche, Cache Stampede, Thundering Herd & Cache Penetration 12. Consistent Hashing with Virtual Nodes (Solving Cache Clustering & Dynamic Scaling) 13. Content Delivery Networks (CDN): Edge Caching, Dynamic Site Acceleration & Origin Shielding

Module 5: Message Brokers, Event-Driven Architecture & Stream Processing

14. Message Queues vs Event Streams: RabbitMQ vs Apache Kafka (Partitioning, Consumer Groups) 15. Exactly-Once Processing Semantics (EOS), Idempotency Keys & Deduplication Architecture 16. Distributed Unique ID Generators: Twitter Snowflake, UUIDv7 & Database Ticket Servers

Module 6: FAANG Classic HLD Architectural Case Studies

17. System Design Case Study 1: URL Shortener (TinyURL / Bitly) at 100M Daily Requests 18. System Design Case Study 2: Distributed Rate Limiter & Web Application Firewall 19. System Design Case Study 3: Real-Time Chat & Notification System (WhatsApp / Slack) 20. System Design Case Study 4: Social Media News Feed (Twitter/Instagram) with Fan-out on Write/Read 21. System Design Case Study 5: Video Streaming Platform (YouTube / Netflix) Transcoding Architecture 22. System Design Case Study 6: Ride Hailing Geospatial Dispatch Architecture (Uber / Ola)

Interactive Lesson Studio

# 13. Content Delivery Networks (CDN): Edge Caching, Dynamic Site Acceleration & Origin Shielding

> High-Level Design (HLD) Notes by Rishabh - Topic 13

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### 1. CDN Architecture (Bringing Data to the User's Doorstep 🌍)

Agar server Virginia, USA me hai aur user Mumbai me hai:
*   Direct Roundtrip: 250ms latency.
*   **CDN (Point of Presence - PoP in Mumbai):** Edge cache se **< 10ms me static assets (JS, CSS, Images, Video chunks)** deliver karta hai!

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### 2. Push vs Pull CDNs

*   **Pull CDN (Default):** Edge server par pehli user request aane par origin server se asset fetch karke cache karta hai (Lazy Caching).
*   **Push CDN:** CI/CD deployment ke waqt naye build assets direct saare globally distributed edge nodes par pre-upload kiye jaate hain.

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### 3. Origin Shielding & Dynamic Site Acceleration (DSA) 🛡️

*   **Origin Shield:** Edge PoPs aur Origin server ke beech ek centralized intermediary caching proxy jo origin database ko 1000 edge nodes ke concurrent fetch load se bachati hai.
*   **Dynamic Site Acceleration:** Route optimization, TCP connection pooling aur BGP routing use karke un-cacheable dynamic API responses ko fastest submarine optical fibers se deliver karna.

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### 4. Master Comparison Matrix

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### 5. Interview Ke 3 Sawal Is Topic Se

1. **Anycast DNS CDN architecture me kaise help karta hai?** -> Saare global edge servers ek hi public IP address announce karte hain; BGP routing user ko geographically nearest internet exchange node par route karti hai.
2. **`Cache-Control: public, max-age=31536000, immutable` header kab use hota hai?** -> Hashed static assets (e.g. `main.a8b1c.js`) ke liye jo browser aur CDN me 1 saal tak safely permanent cache rehte hain.
3. **Stale-While-Revalidate header CDN par kya karta hai?** -> User ko instantly cached stale asset serve karta hai jabki background me asynchronously origin server se fresh copy update karta hai.

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**Next Topic:** 14. Message Queues vs Event Streams: RabbitMQ vs Apache Kafka (Partitioning, Consumer Groups)

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