CloudFront vs Fastly

AWS CloudFront and Fastly are both premium CDN platforms, but they serve different audiences. CloudFront is the default CDN for AWS users. Fastly is built for engineering teams that need granular cache control, instant purging, and powerful edge compute.

Cache Purge Speed — Fastly's Differentiator

Fastly can purge cached content globally in approximately 150 milliseconds. This is dramatically faster than CloudFront's invalidation, which takes seconds to minutes. For news sites, e-commerce platforms, and any application where content changes frequently, Fastly's instant purge means users always see fresh content without waiting.

Cache Control

Fastly uses VCL (Varnish Configuration Language) for cache configuration, giving engineers programmatic control over every aspect of caching: custom cache keys, conditional logic based on headers, cookies, or geo-location, and fine-grained TTL management. CloudFront's cache behaviors are simpler but less flexible.

Edge Compute

Fastly's Compute@Edge runs WebAssembly at the edge, supporting Rust, Go, JavaScript, and other languages that compile to Wasm. It offers sub-millisecond cold starts and full request/response manipulation. Lambda@Edge supports Node.js and Python with higher cold starts (milliseconds to seconds) and more restrictive execution limits.

Real-Time Observability

Fastly streams logs in real time to any endpoint (S3, BigQuery, Datadog, Splunk). CloudFront sends logs to S3 (delayed) or Kinesis Data Streams (near-real-time). For debugging production issues, Fastly's observability is superior.

For CDN architecture decisions, explore our concepts and system design interview guide. See interview questions and pricing.