Amazon CloudFront CDN
Amazon has released their CDN offering, CloudFront. Some interesting notes:
- Eight POPs in the US, four in Europe and two in Asia.
- Pricing is different across regions - i.e. Asia is more expensive than the US - and charged by GB’s delivered and GET requests.
- Origin must be S3, although the way the documentation reads and is structured, sounds like they could allow your own origin in the future
- Works on a pull model. I.e. when a user requests the object from CloudFront, if CloudFront doesn’t have it in cache, it will go to S3 to grab object, serve object to user and cache it.
- Objects expire in 24 hours by default, although Amazon somewhat honors Expires/Cache-Control Headers as long as they don’t go below 24 hours
- Amazon is using LRU (Least Recently Used) to evict objects. I.e. the photo of your cat that gets viewed once every 20 hours may get removed from cache when more popular objects fill up the cache
- No way to purge or invalidate objects in cache on CloudFront - Amazon recommends using filename versioning to overcome this limitation
- You can CNAME your hostname to CloudFront
It is a very, very basic CDN offering and I am interested to see the level of uptake. Since Amazon requires a person to use S3, it will also be interesting to see the true
cost of using S3 combined with CloudFront, compared with using another CDN vendor and your own origin infrastructure.