As mentioned in my original comment, if someone isn’t comfortable showing me the source code I simply ask for them to describe how it works, challenges in building it, how they built it, etc.
I could do this and would welcome this type of interview experience. I'd be able to talk in general terms about the problems I work on and their solutions but not the low level specifics.
To add some context, my work is in Financial Services, trading systems and whatnot.
To add some context, my work is in Financial Services, trading systems and whatnot.