Find the k most similar items in a 10M-vector index without a hosted service.
Brute force is O(N*d) per query and dies at ten million vectors. The answer is approximate nearest neighbor: trade a little recall for orders of magnitude less work, and know exactly which knob buys what.
Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.
Brute force is O(N*d) per query and dies at ten million vectors. The answer is approximate nearest neighbor: trade a little recall for orders of magnitude less work, and know exactly which knob buys what.
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.
