Scaling for Query Latency

Latency of a single query is determined by the slowest component in the query execution path. It is sometimes correlated with throughput, but not always — throughput and latency are opposite tuning directions.

Low latency optimization is aimed at utilising maximum resource saturation for a single query, while throughput optimization is aimed at minimizing per-query resource usage to allow more parallel queries.

Performance Tuning for Lower Latency

• Increase segment count to match CPU cores (default_segment_number: 16) Minimizing latency
• Keep quantized vectors and HNSW in RAM: memory: pinned on Qdrant 1.19 or newer, always_ram: true on 1.18 or older
• Reduce hnsw_ef at query time (trade recall for speed) Search params
• Use local NVMe, avoid network-attached storage

Memory Pressure and Latency

RAM is the most critical resource for latency. If working set exceeds available RAM, OS cache eviction causes severe, sustained latency degradation.