CDN concept and usage in HLD - Architecture Diagram

System Overview - CDN concept and usage

A Content Delivery Network (CDN) is a system of distributed servers that deliver web content to users based on their geographic location. It improves website speed, reduces latency, and handles high traffic by caching content closer to users.

Architecture Diagram

User
  |
  v
+----------------+
|      CDN       |
| (Edge Servers) |
+----------------+
  |
  v
+----------------+
| Load Balancer  |
+----------------+
  |
  v
+----------------+       +------------+
|   Web Server   |<----->|   Database |
+----------------+       +------------+

Components

User

client

Requests content from the system

CDN

cdn

Caches and delivers static content from edge servers close to users

Load Balancer

load_balancer

Distributes incoming requests evenly across web servers

Web Server

service

Serves dynamic content and handles business logic

Database

database

Stores persistent data for the application

Request Flow - 8 Hops

User → CDN

CDN → CDN

CDN → Load Balancer

Load Balancer → Web Server

Web Server → Database

Web Server → Load Balancer

Load Balancer → CDN

CDN → User

Failure Scenario

Component Fails:CDN

Impact:Users experience slower content delivery as requests go directly to origin servers, increasing latency and load on origin infrastructure.

Mitigation:System falls back to origin servers directly; origin infrastructure must be scaled to handle increased load until CDN is restored.

Architecture Quiz - 3 Questions

What is the main purpose of the CDN in this architecture?

A To balance load between web servers

B To store user data permanently

C To cache and deliver content closer to users

D To process database queries

Design Principle

This architecture shows how a CDN reduces latency and load on origin servers by caching content close to users. It also demonstrates the importance of load balancing for distributing requests and the fallback mechanisms when caches miss or components fail.