When Junk Dimensions Grow

The follow-up the interviewer uses to probe depth: 'What happens when the business adds three more flags next quarter?' This tests whether you have thought about the combinatorial growth of junk dimensions and know when to split them. The Math the Interviewer Will Make You Do When to Split: The Threshold You Should Name The Follow-Up Trap The interview-winning answer for explosion: 'Junk dimensions work when the product of cardinalities stays under about 1,000. Beyond that, I would split into multiple junk dimensions grouped by domain: dim_order_flags for shipping/gift booleans, dim_payment_flags for payment-related codes. Each stays small.'