Ever since Digg launched its new site design, it’s been plagued with all kinds of trouble, not least of which is that it keeps going down. The problems with the new architecture are so bad that VP of Engineering John Quinn is now gone, we’ve confirmed with sources close to Digg.

In a Diggnation video today, CEO Kevin Rose explained some of the technical issues the site is dealing with and why it can’t simply roll back to the previous architecture. The new version of Digg, v4, is based on a distributed database called Cassandra, which replaced the MySQL database the site ran on before. Cassandra is very advanced—it is supposed to be faster and scale better—but perhaps it is still too experimental. Or maybe it’s just the way Digg implemented it (Twitter uses Cassandra, although not for its main data store, as does Facebook in places, but it obviously is not as battle-tested as it needs to be). Every engineer at Digg is currently just trying to keep the site up and running.

Quinn was the main champion of moving over to Cassandra, say our sources. Now the site is taking a huge hit, at least in the short term, because of that decision and/or how it was implemented, and Quinn is paying for it with his job. But it is not clear what else Digg should have done. Digg was originally built on the tried-and-true LAMP stack (Linux, Apache, MySQL, PHP) of open-source technologies, but it was straining under the load of Digg’s traffic. Replacing MySQL with Cassandra was supposed to help fix that. It came with its own set of larger problems instead.

Quinn joined Digg nearly three years ago. Before that, he was VP of engineering at SquareTrade and a software engineer at Oracle. It is not clear who will replace him at Digg.