How To Optimize Your Site With HTTP Caching

[bitops]

This is a good writeup, though I'm surprised no-one has mentioned the holy grail of caching with HTTP. That of course is good old RFC 2616: http://www.ietf.org/rfc/rfc2616.txt

There's an entire section in there devoted just to caching in HTTP. Very well worth reading in its entirety.

[d0mine]

http://tools.ietf.org/html/rfc2616 adds errata, RFCs that update it and hyperlinks (it is a web after all)

Direct link to Caching in HTTP http://tools.ietf.org/html/rfc2616#section-13

[ceol]

This is a great article for an introduction to HTTP caching. It's well-written and even covers how to set up caching in Apache.

[kalid]

Thanks for the kind words (I'm the author). My main, ever-evolving goal when writing tutorials is to try to write what I'd like to see:

1) Explain the underlying concept

2) Show variations

3) Explain how to do it yourself

4) Show how to verify you did it correctly

5) Meta: be as concise as possible, maximize bang for the buck

[fexl]

And it links to another great article on gzip compression.

[js2]

Be careful with ETags if you're serving content from a web-farm - http://developer.yahoo.com/performance/rules.html#etags

[riledhel]

In the same spirit, there's a lot to gain and very little to lose if you activate ETags and serve content from just one source.

[js4all]

A pretty basic write up. Static caching is standard these days. The article doesn't help with speeding up today's dynamic sites.

[ehc]

Article from 2007

[kalid]

Yep, I was surprised too to see it on HN :).

I think one of the meta-takeaway is that understanding the fundamentals of web caching can help with your general CS knowledge ("There are only two hard problems in Computer Science: cache invalidation and naming things." -- Phil Karlton).

Looking at Apache, we see a few strategies:

  * Include last-modified metadata
  * Include content metadata (eTag/md5 of content)
  * Include explicit expiration date
  * Include a max-age
  * Include metadata about who can cache (public/private/no-caching, i.e. users can cache but proxies cannot)

These approaches could be used when designing data flows with Memcache, Redis, etc.

[bittermang]

Good information doesn't necessarily have an expiration date, but I concede to your point that it might not be the most up to date source out there.

[oniTony]

2008+ version -- throw your assets into CloudFront (or another CDN of choice), let CDN handle the caching. ;)