qdrant-scaling-query-volume

$npx mdskill add github/awesome-copilot/qdrant-scaling-query-volume

Reduce transfer costs by sampling shards for large queries.

  • Handles queries with high limits and multiple shards.
  • Depends on Qdrant auto-sharding and Poisson statistics.
  • Calculates smaller per-shard limits using a safety factor.
  • Merges sampled results to deliver complete answers.
SKILL.md
.github/skills/qdrant-scaling-query-volumeView on GitHub ↗
---
name: qdrant-scaling-query-volume
description: "Guides Qdrant query volume scaling. Use when someone asks 'query returns too many results', 'scroll performance', 'large limit values', 'paginating search results', 'fetching many vectors', or 'high cardinality results'."
---

# Scaling for Query Volume

Problem: When a query has a large limit (e.g. 1000) and there are multiple shards (e.g. 10), naively each shard must return the full 1000 results — totaling 10,000 scored points transferred and merged. This is wasteful since data is randomly distributed across auto-shards.

## Core idea

Instead of asking every shard for the full limit, ask each shard for a smaller limit computed via Poisson distribution statistics, then merge. This is safe because auto-sharding guarantees random, independent data distribution.

## When it activates

- More than 1 shard
- Auto-sharding is in use (all queried shards share the same shard key)
- The request's limit + offset >= SHARD_QUERY_SUBSAMPLING_LIMIT (128)
- The query is not exact

## Key tradeoff

 The strategy trades a small probability of slightly incomplete results for a large reduction in inter-shard data transfer, especially for high-limit queries across many shards. The 1.2x safety factor and the 99.9% Poisson threshold keep the error rate very low — comparable to inaccuracies already introduced by approximate vector indices like HNSW.
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