That is wrong. You should be eminently prepared for this question. At the very least, you should have estimated the scale you need to be able to support, and demonstrate that your systems can handle the load. This means spending development time and effort to create a scaling test environment, with instrumentation, and then spending time to present the results.
Didn't mean to sound dismissive. My reply wasn't stating that we're unprepared; we're absolutely prepared and we think about this ALL DAY. We're also seasoned enough to know that behaviors sometimes deviate from test environments while in the wild.
