CDN for high traffic flash sales

For flash-sale traffic, I’d shortlist Cloudflare, Amazon CloudFront, and Fastly. The CDN alone isn’t enough—you want strong caching plus protection against the surge reaching your origin.

• Cloudflare CDN — a strong general-purpose choice. Its edge network caches content close to users, and Tiered Cache can reduce repeated requests hitting your origin. Cloudflare also provides DDoS protection and load balancing.Cloudflare Docs+1
• Amazon CloudFront — particularly attractive if your stack is already on AWS. Origin Shield + regional/edge caching can collapse large numbers of requests into far fewer origin requests, and AWS explicitly documents CloudFront for sudden traffic spikes and flash crowds.AWS Documentation+1
• Fastly — worth considering when you need highly programmable edge behavior and sophisticated real-time traffic handling. Fastly specifically describes predictive scaling for spikes such as flash sales and supports stale-content fallbacks when origins have problems.Fastly

My practical recommendation

If you're starting from scratch, Cloudflare is probably the simplest choice. If you're already heavily invested in AWS, CloudFront + Origin Shield is a natural fit.

For a flash sale, I'd also configure:

1. Aggressive caching for product images, CSS, JS, and sale/landing pages.
2. Tiered caching / Origin Shield to prevent cache misses from stampeding the origin.
3. Separate, carefully protected paths for checkout, cart, inventory, and payment APIs—these generally can't simply be cached.
4. Rate limiting/bot protection so automated buyers don't consume the capacity needed by real customers.
5. Origin autoscaling and load balancing; a CDN cannot compensate for an origin that collapses when dynamic requests spike.

If you tell me your stack (e.g. AWS, Azure, GCP, Shopify, Kubernetes, or bare-metal) and approximate peak traffic (requests/sec or concurrent users), I can narrow this down to an architecture and configuration.