http://highscalability.com/blog/2011/6/27/tripadvisor-architecture-40m-visitors-200m-dynamic-page-view.html

request URL is parsed, content collected from various services, and then applied to a template

request routed to load balancer in front of cookie-based web server pool, pool can help for deployment, A/B testing, server are stateless

services are essentially large intelligent cache in front of database

DB: postgres, 6 DRDB pair for high availability

infrastructure to select code / template path based on request context

TripAdvisor architecture 2011/06