What software do you use to perform A/B tests?
This question usually gets one of two specific groups of answers. In the first group, you have what I'd call the 'enterprise' platforms: Adobe Target, FullStory, Optimize, etc. In the second group, you have the 'startup' platforms: ClickFunnels, Google Experiments, Unbounce, and other freemium platforms. The interviewing is trying to understand if your background in CRO software matches what they have or can afford.
"In the past, I've worked exclusively with startups and SMBs on conversion rate optimization, so the software I recommend includes a combination of Google Experiments and Unbounce, along with the A/B testing platform provided by your email service provider. That should let us test the key components of your marketing strategy without breaking the bank."