has been quietly racking up a lot of success for its cloud-for-hire, Heroku.

Heroku launched its one millionth live app, the company said. That's some pretty fair progress. bought Heroku for $212 million in cash in December, 2010. At that time, Heroku was hosting 105,000 apps.

Heroku isn't exactly like Amazon's EC2, which simply lets companies host already-finished apps on Amazon's servers.

It's in the "platform as a service" category, meaning that it offers more high-level functions so developers have to do less work -- similar to Microsoft's Windows Azure. While Amazon's EC2 offers access to shared servers and an operating system of choice (Windows, Linux), Heroku hosts apps built with specific languages (Java and Ruby).

Heroku is one of four clouds from and the company has just released some impressive 2011 overall stats:

"3,000 apps were built or installed every 24 hours…that’s one every 30 seconds," said Andrew Leigh in a blog post. "Our platform executes more than 650 million transactions per day…that’s 7,500 transactions per second."

Not bad.