Pushing dynamic content via AJAX and caching the much larger part of the page that isn't dynamic is a great tip -- much better than caching fragments. I will now steal it and appear smart by telling others. :-P
Make sure you run your specific implementation past an SEO who knows what they're doing -- and on this issue, most don't. (The sweet spot is probably caching the whole page for non logged-in users and regenerating that "relatively infrequently", and doing the AJAX trick for your logged-in users only.)
"The Varnish Guy", as many call him here and on reddit is none other than Poul-Henning Kamp, Yeah, that phk from FreeBSD. So, yeah, you're gonna get some top-notch systems engineering from him.
Varnish is most definitely a huge win. It can be somewhat of a pain to install if you're not using Chef or something, though. Here's some helpful info I compiled that might come in handy for first-timers:
Installing Varnish with nginx, Passenger, and Monit on Ubuntu 8.10 intrepid:
Happy to see varnish get so much airtime recently, it's a great piece of software and I would not be able to run my service at the current budget without it. If you are not a varnish user yet and you have a high volume site, go check it out, and save yourself some big $ by better utilizing the servers that you already have.
Varnish is very attractive, and it is something that my organization is beginning to look at.
But, this appears to be a new blog from Posterous, with this submission being it's first post, and it comes to HN just after Posterous had some, well potentially negative press about their traffic.
Am I off base in asserting that this blog post is a marketing play? And if this isn't their first blog post, please let me know of my grave error (and down-vote me accordingly)
Edit and follow-up: This blog has been around for a while, so I guess I'll sit back and relax. However, I'll still stand behind the marketing assertion.
Their description of Lacquer sounds problematic to me.
The usual failure case for this is that a cache node goes down for awhile, misses some invalidation messages, then comes up and starts serving (stale) traffic again.
This case isn't so bad if you keep your TTL low, and have cheap page revalidation.
Interesting, we also added a Varnish based cache layer and also got a dramatic performance boost. The connections to the backend dropped to 50%, taking off a lot load.
I am currently going through your VCL to take some ideas for improvement. Thanks for posting that.
