Recall-vs-Latency Tradeoff

The recall-vs-latency tradeoff describes the fundamental tension in ANN search: higher recall — returning more of the true nearest neighbors — requires examining more candidates, which increases query time. Index construction parameters such as HNSW's ef_construction and ef_search, or IVF's nprobe, control where on this curve a system operates. Production teams typically measure recall at the target latency percentile and tune parameters to meet a minimum recall threshold within a latency budget.