[esafak]

It would take a very senior coder to be able to make sense of the code base and start fixing a bug in the duration of an interview.

Plus the code base will involve technologies they are not familiar with; rarely does everyone know every technology needed beforehand.

[bilsbie]

To clarify I’d intend the interviewer to do most of work that requires inside knowledge.

The interviewee could suggest the specific implementations within that.

Eg. We need to hook into our fubu system. Here’s our library for that. How would you code that?