A couple interesting things coming out of startup land.
For one, Posterous has a little writeup on Building and Scaling a Startup on Rails: 12 Things We Learned the Hard Way. Good things to take away include using Sphinx/Solr for search, but the real important takeaway for the MySQL crowd is Storage engine matters, and you should probably use InnoDB. If you’re writing an application, know your storage engines. There are also bits to tell you how to use query_viewer and New Relic to help you fix database bottlenecks, use memcached later, and more. Its a great read.
Next up, there’s How FriendFeed uses MySQL to store schema-less data. I hope Bret from FriendFeed writes more on their infrastructure over time. Its interesting to see that they thought of going the CouchDB route, but never saw it as “proven” technology (in comparison to MySQL).