CI tends to have non linear usage behavior: Minor use in the beginning of the project, and massive use in the end of the day and just before releasing the new version.
During these peak hours TeamCity can launch on demand instances, running the build and the tests and shut down the instances when it ends.
Bottom Line
It is a fine example of how development teams can keep their infrastructure costs as low as possible, while maintaining maximum flexibility.
Keep Performing,
Moshe Kaplan
