qdrant-minimize-latency

# 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](https://search.qdrant.tech/md/documentation/operations/optimize/?s=minimizing-latency) - Keep quantized vectors and HNSW in RAM (`always_ram=true`) - Reduce `hnsw_ef` at query time (trade recall for speed) [Search params](https://search.qdrant.tech/md/documentation/operations/optimize/?s=fine-tuning-search-parameters) - 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. - Vertical scale RAM first. Critical if working set >80%. - Use quantization: scalar (4x reduction) or binary (16x reduction) [Quantization](https://search.qdrant.tech/md/documentation/manage-data/quantization/) - Move payload indexes to disk if filtering is infrequent [On-disk payload index](https://search.qdrant.tech/md/documentation/manage-data/indexing/?s=on-disk-payload-index) - Set `optimizer_cpu_budget` to limit background optimization CPUs - Schedule indexing: set high `indexing_threshold` during peak hours ## Vertical Scaling for Latency More RAM and faster CPU directly reduce latency. See [Vertical Scaling](../scaling-data-volume/vertical-scaling/SKILL.md) for node sizing guidelines. ## What NOT to Do - Do not expect to optimize latency and throughput simultaneously on the same node - Do not use few large segments for latency-sensitive workloads (each segment takes longer to search) - Do not run at >90% RAM (cache eviction causes severe latency degradation that can last days) - Do not ignore optimizer status during performance debugging - Do not scale down RAM without load testing (cache eviction causes days-long latency incidents)