Databases for startups

I see over and over again that "Relational databases are not easily scalable. It will require a lot of efforts to build a scalable and redundant setup." I would like to see more mention of how many users/rps/etc you can handle with a maximally sized Amazon RDS redundant instance.<p>Scalable is different than infinitely scalable. Scalable used to mean, for example, being able to get a close-to-linear speedup from multiple cores, more or faster disks, etc.

We've built a clustered, infinitely scalable, fault tolerant, fault-tolerant database system that supports full relational and ACID semantics. It also emulates the MySQL protocol, so it's very drop-in. <a href="http://www.clustrix.com" rel="nofollow">http://www.clustrix.com</a><p>(sorry to sound like an ad, but we really do have a great solution for this)