CDN

Content Delivery Network (CDN) is a distributed proxy server that cache website static content closer to users. This routing visitor requests to the nearest edge server rather than the main origin server. CDNs can reduce latency and increase page loading speed, and protect websites from traffic spikes and DDoS attacks

Pull CDN

sequenceDiagram
    actor User
    participant Edge as CDN Edge
    participant Origin as Origin Server
    User->>Edge: Request asset
    alt Cache hit
        Edge-->>User: Return cached asset
    else Cache miss
        Edge->>Origin: Fetch asset
        Origin-->>Edge: Return asset
        Note over Edge: Cache asset
        Edge-->>User: Return asset
    end

• Advantages:
  • simple setup
  • automatic distribution
  • storage only for requested content
• Trade-offs:
  • the first request at each edge location is slower and creates origin traffic
  • stale content may require cache invalidation or versioned URLs.
• Best for: websites with large or frequently changing content libraries and unpredictable access patterns.

Push CDN

sequenceDiagram
    actor Owner as Content Owner
    participant CDN as CDN Storage
    participant Edge as CDN Edge
    actor User
    Owner->>CDN: Upload asset
    CDN->>Edge: Distribute asset
    User->>Edge: Request asset
    Edge-->>User: Return asset

• Advantages:
  • no cache-miss request to the origin
  • predictable availability
  • direct control over which files and versions are distributed
• Trade-offs:
  • publishing and invalidation must be managed explicitly
  • unused content may consume CDN storage.
• Best for: static and versioned assets, large downloads, software releases, and files that must be available immediately at the edge.

Comparison