Describe heuristic evaluation and two heuristics that guide UI components

WHAT THIS TESTS: This question checks whether you treat usability as an engineering constraint rather than a design afterthought. Senior engineers are expected to know how to evaluate interfaces systematically and to justify component-level choices with established UX principles instead of personal taste.

A GOOD ANSWER COVERS: First, define heuristic evaluation as an expert review method where trained evaluators or developers inspect a user interface against a set of broad rules of thumb to find usability problems without running a full user study. Second, select two heuristics from the Nielsen Norman Group ten and map each directly to a component decision. A strong pairing is Visibility of System Status and Error Prevention. For Visibility of System Status, explain that the component must communicate its state immediately through appropriate feedback within a reasonable time, such as showing a loading skeleton during data fetch, a progress bar during file upload, or a success toast after completion, so users know the system received their input and is working. For Error Prevention, explain that the component should add guardrails rather than relying solely on error messages after the fact, such as disabling a submit button until form validation passes, using constraints to prevent invalid input, or adding a confirmation dialog before a destructive delete action. Third, briefly note that heuristic evaluation is inexpensive and fast compared to user testing, making it useful early in the development cycle when you want to catch obvious issues before shipping code to users.

COMMON WRONG ANSWERS: Confusing heuristic evaluation with A/B testing, analytics, or user interviews. Naming vague principles like make it intuitive or keep it clean that are not among the established NN/G heuristics. Listing heuristics without connecting them to concrete component states, props, event handlers, or interactions. Claiming that heuristics replace user research rather than complement it, since expert reviews do not capture real user mental models or edge cases.

LIKELY FOLLOW-UPS: How would you prioritize fixes if a heuristic evaluation surfaces twenty issues? When would you choose heuristic evaluation over usability testing with real participants? Can you give an example where following a heuristic too rigidly actually hurt the user experience? How do you apply these principles consistently across a design system or component library?

ONE CONCRETE EXAMPLE: Consider a bulk delete button inside a data table. Applying Visibility of System Status means the button enters a processing state, the affected rows dim immediately after click, and a toast confirms completion so users know the system is working and when it is done. Applying Error Prevention means the button is disabled when no rows are selected, a confirmation modal requires typing the number of items to be deleted, and the modal defaults to cancel rather than confirm, preventing accidental data loss.

Source: nngroup.com