How do you detect and prevent benchmark contamination, and why are public LLM leaderboards often inflated?
When a benchmark leaks into pretraining, the score measures memorization rather than ability. The signal is the detection methods (n-gram overlap, canaries, perturbation tests) and why fresh held-out evals matter.
Updated Sep 2026 · Grounded in real GenAI, LLM, and AI/ML engineering interview loops and written to a senior-engineer editorial bar.
When a benchmark leaks into pretraining, the score measures memorization rather than ability. The signal is the detection methods (n-gram overlap, canaries, perturbation tests) and why fresh held-out evals matter.
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.
