Check out memcached, if you're into researching ways of making your web apps speedy through clever database caching. (used by LiveJournal, Slashdot, Wikipedia, SourceForge). Very very cool.
By having your app first check the memcache instead of going to the database directly, you reduce the overhead that is inherent with ACID properties in relational database management system transactions. --as I understand it from reading about it on a few sites, by hashing database records in a cache reading from that hash where possible and updating the hash when that data is not available, you end up greatly reducing the demand on the database.
Makes me excited to think about the possibilities of an upcoming RESTful Rails app deployed on an clustered Ubuntu instance on EC2, utilizing memcached, that is Gears-enabled for offline capability as well... whoops, I wandered off...
Here's some info on memcached. I'm going to definitely check it out and try to implement:
memcached is a high-performance, distributed memory object caching system, generic in nature, but intended for use in speeding up dynamic web applications by alleviating database load.