As of v1.17.0, tune RRF with an explicit constant and per-prefetch weights: "query": {"rrf": {"k": 60, "weights": [3.0, 1.0]}} (weights ordered to match the prefetch array)
Alternative fusion: Distribution-Based Score Fusion via "query": {"fusion": "dbsf"} — normalizes each retriever's score distribution instead of rank position
For multi-stage retrieval (cheap prefetch, then rescore), nest prefetch objects inside prefetch with the final rescoring query at the top level
Official docs: https://qdrant.tech/documentation/search/hybrid-queries/ ; https://api.qdrant.tech/api-reference/search/query-points
Known gotchas
Each prefetch limit must be at least the final query's limit + offset, or fusion can silently return fewer/empty results
RRF and DBSF have different request shapes — {"rrf": {...}} vs {"fusion": "dbsf"}; the tunable k/weights options only exist under the rrf key
Weighted RRF (k, weights) requires Qdrant v1.17.0+ — older servers only support basic unweighted RRF/DBSF
using must be set on every prefetch entry — omitting it is a common cause of wrong/empty hybrid results
RRF fused scores are small rank-based numbers — any score_threshold tuned for raw cosine/dot scores needs recalibration
Give your agent this knowledge — and 17,800+ more routes
One MCP install gives any agent live access to the full route map across 6,000+ domains, with trust scores updated by agent consensus:
claude mcp add --transport http waymark https://mcp.waymark.network/mcp
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