Why Use a CDN?
Content Delivery Networks cache static assets at 100+ edge locations, cutting latency by 50-80%, reducing origin bandwidth 60-90%, and absorbing DDoS attacks before they hit your server.
Choosing a Provider
Cloudflare – free tier, unmetered DDoS, global anycast. AWS CloudFront – pay-per-GB, tight integration with S3 and ALB. KeyCDN – low-cost, $0.04/GB, good for bootstrappers. Akamai – enterprise, SLA, premium pricing.
Integration Steps
- Sign up, add domain, note assigned edge hostnames (e.g., dxx.cloudfront.net)
- Change DNS A/AAAA or CNAME root/www to edge hostname
- Configure SSL: either Cloudflare issues Shared cert or upload custom cert to AWS
- Set cache rules: .html 5 min, .jpg 1 day, /api/* bypass
DNS Configuration Modes
Full (orange cloud): traffic proxies through CDN, hides origin IP. DNS-only (gray): you control IP but lose caching. Use Full for public sites, DNS-only for MX/subdomains that shouldn’t proxy.
Origin Headers
Send Cache-Control: public, max-age=3600 to instruct edge cache. For dynamic content use Cache-Control: private, no-store or leverage edge workers to cache logged-in state carefully.
Cache Invalidation
Cloudflare offers purge by URL, tag, or entire zone. AWS invalidation paths cost $0.005 each after 1,000 free/month. Use versioning (?v=2) on assets to avoid frequent purges.
Security Hardening
Enable WAF rules (OWASP core), rate-limit (60 requests/min per IP), and bot fight mode. Upload custom firewall rules to block country codes if compliance requires geo-fence.
Analytics & Logs
Cloudflare Analytics shows bandwidth saved, threats blocked, and edge response time. Pipe logs to AWS S3 or Datadog for correlation with origin errors.
Multi-CDN Strategy
Large enterprises use NS1 or Traffic Director to steer users to fastest CDN via RUM data. Adds complexity but guarantees 99.99% uptime even if one CDN has global outage.
Cost Optimization
Compress images to WebP, minify CSS/JS, enable Brotli at edge, and set aggressive cache on fonts. A 1 MB hero image cached at 300 edge locations serves 10k requests for <1 GB origin transfer.