Amazon CloudFront

Amazon CloudFront is AWS's global content delivery network (CDN). It caches static and dynamic content at 600+ edge locations and regional edge caches, terminates TLS close to users, and can execute lightweight code at the edge — reducing latency and offloading traffic from origin servers.

Key Features:

• Global Edge Network: Points of Presence on six continents serve cached content from the nearest location to the user.
• Multiple Origin Types: S3 buckets (with Origin Access Control), custom HTTP origins, Application Load Balancers, API Gateway, MediaStore, MediaPackage.
• Cache Policies & Origin Request Policies: Decouple cache-key construction from headers forwarded upstream — essential for cache hit rates.
• CloudFront Functions: Sub-millisecond JavaScript at viewer request/response for URL rewrites, header manipulation, A/B routing.
• Lambda@Edge: Full Node.js/Python functions at four lifecycle hooks — heavier than CloudFront Functions but far more capable.
• TLS & ACM Integration: Free certificates via ACM, SNI support, modern ciphers, HTTP/2 and HTTP/3.
• Origin Shield: Extra regional cache layer that further reduces origin load and improves cache hit ratio.
• Signed URLs & Cookies: Time-limited, restricted access to private content.
• AWS WAF & Shield Integration: L7 firewall rules and DDoS mitigation at the edge.

Common Use Cases:

• Static Website Hosting: S3 + CloudFront + ACM is the canonical pattern for serving SPAs and marketing sites globally.
• Dynamic API Acceleration: Terminate TLS at the edge and use long-lived connections to origin for lower latency.
• Video Streaming: HLS/DASH delivery for live and VOD workflows.
• Software & Package Distribution: Cache large binaries (container layers, installers, model weights) close to users.
• Security Edge: Enforce bot rules, geo-blocking, and rate limiting via WAF before traffic reaches origins.

Tips for High Cache Hit Ratio:

• Minimize cache-key dimensions — only include headers and query strings that actually vary the response.
• Set sensible Cache-Control headers at the origin; CloudFront honors them.
• Normalize query strings (sort keys, strip tracking params) in a CloudFront Function.
• Use Origin Shield for origins with modest traffic spread across many POPs.
• Monitor with CloudFront reports and CloudWatch metrics — look at cache hit ratio, 4xx/5xx rate, and origin latency.