This is a bit of an oddball question, but:
If a something is "scalable", it means that regardless of how intense the requirements ever get, the product/service/technology/whatever will be able to satsify those requirements.
If a something is "robust", it means that it works reliably under a variety of different working environments.
What's the word that means "helps to ensure that humans don't accidently break something"
Example: You didn't give an employee root FTP access to your web server not because you don't trust them, but because it increases the [word goes here!] of the system.
It's like security...but security implies that you're trying to keep bad guys out. What's the one that means that you're trying to stop good guys from breaking something?
(This is something that keeps coming up at meetings, and I have no word to explain what I'm talking about.)