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Hybrid RAG with Knowledge Graph Query Router

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TL;DR

Hybrid RAG is a Retrieval-Augmented Generation architecture that combines traditional vector (dense) search with a Knowledge Graph to capture both factual lookups and relational connections between data, using a Query Router to dynamically decide which retrieval path to invoke. It addresses a core limitation of pure vector RAG systems that retrieve semantically similar chunks in isolation but fail on questions requiring understanding of relationships between entities. Pure vector search retrieves individually relevant chunks but cannot answer questions that span relationships between entities (e.g., 'How does a pricing plan affect support options?'). A Knowledge Graph captures entity relationships, while a Query Router intelligently directs queries to the right retrieval path, yielding more accurate and context-aware answers from LLM pipelines.

What it actually is

  • What: Hybrid RAG is a Retrieval-Augmented Generation architecture that combines traditional vector (dense) search with a Knowledge Graph to capture both factual lookups and relational connections between data, using a Query Router to dynamically decide which retrieval path to invoke. It addresses a core limitation of pure vector RAG systems that retrieve semantically similar chunks in isolation but fail on questions requiring understanding of relationships between entities.
  • Who built it / maintained by: Architectural pattern popularized by the AI/ML community; most prominent production implementation by Microsoft (GraphRAG, open-sourced 2024); also implemented via LlamaIndex and LangChain ecosystems
  • Status: stable
  • Why it matters: Pure vector search retrieves individually relevant chunks but cannot answer questions that span relationships between entities (e.g., 'How does a pricing plan affect support options?'). A Knowledge Graph captures entity relationships, while a Query Router intelligently directs queries to the right retrieval path, yielding more accurate and context-aware answers from LLM pipelines.
  • How it compares to alternatives:
  • Naive/vanilla RAG (vector-only)
  • GraphRAG (Microsoft)
  • LlamaIndex Knowledge Graph Index
  • LangChain GraphCypherQAChain
  • Neo4j GraphRAG Python
  • Amazon Neptune + RAG
  • NebulaGraph LLM integration
  • GitHub stars: 32,747 · License: MIT · Archived: no

Links

  • Repo: https://github.com/microsoft/graphrag
  • Docs: https://microsoft.github.io/graphrag/

Kickstarter guide

Install Microsoft GraphRAG via pip install graphrag and index your documents with python -m graphrag.index --root ./your_project. For a hybrid vector + graph setup in LlamaIndex, combine a KnowledgeGraphIndex with a VectorStoreIndex under a RouterQueryEngine that picks the best retriever per query. Neo4j's neo4j-graphrag-python package (pip install neo4j-graphrag) offers a ready-made hybrid pipeline with built-in query routing between Cypher-based graph traversal and vector similarity search.