Refactor a 500-line function that parses, computes, and prints into unit-testable pieces without changing behavior. Walk me through it.
Most candidates start rewriting. The interviewer is grading whether you isolate pure logic from side effects before you touch a line, because that is the difference between a safe refactor and a silent behavior change.
Updated Sep 2026 · Grounded in real GenAI, LLM, and AI/ML engineering interview loops and written to a senior-engineer editorial bar.
Most candidates start rewriting. The interviewer is grading whether you isolate pure logic from side effects before you touch a line, because that is the difference between a safe refactor and a silent behavior change.
Lead with where the obvious approach breaks, because that is the judgment they are screening for — most candidates jump straight to the happy path and lose the room.
Then walk the failure back through the pipeline in order, naming the one metric the customer's exec sponsor actually cares about before you propose the fix.
