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Database / Qdrant Vector DB Interview questions

Explain the execution flow of a RAG pipeline built with Qdrant as the retrieval layer?

A retrieval-augmented generation pipeline using Qdrant separates cleanly into an ingestion phase, run once or incrementally as new content arrives, and a query-time phase, run for every user request, with Qdrant's collection serving as the shared retrieval index connecting the two.

flowchart TD subgraph Ingestion A[Source documents] --> B[Chunk into passages] B --> C[Generate dense - and optionally sparse - embeddings per chunk] C --> D[Upsert points: vectors + payload metadata into Qdrant collection] D --> E[Create payload indexes on frequently filtered fields] end subgraph Query Time F[User question] --> G[Embed the question - dense/sparse as configured] G --> H[query_points: vector search + payload filter, optionally hybrid via Prefetch/Fusion] H --> I[Retrieve top-k relevant chunks with payload] I --> J[Construct prompt: question + retrieved chunks as context] J --> K[LLM generates grounded answer] end

During ingestion, documents are chunked, embedded, and upserted into a Qdrant collection with payload metadata like source, date, or category, alongside payload indexes for any fields the application expects to filter on later, such as restricting retrieval to a specific tenant or document category.

At query time, the user's question is embedded the same way, and Qdrant's query_points retrieves the most relevant chunks — combining vector similarity with any applicable payload filters, and optionally fusing dense and sparse retrieval via Prefetch and a fusion method for hybrid search — before those retrieved chunks are inserted into a prompt as grounding context for the LLM to generate its final, evidence-based answer.

What happens during ingestion before points are stored in Qdrant?
What can be combined with vector similarity during query-time retrieval?

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