Basic RAG has limitations. Advanced patterns address them.
HyDE (Hypothetical Document Embeddings): Generate hypothetical answer, embed that, search. Better for question-to-document matching.
Query Expansion: Rephrase query multiple ways. Search with each. Merge results.
Reranking: Retrieve top-, rerank with cross-encoder model, take top-. More accurate but slower.
Parent Document Retrieval: Embed small chunks, return parent document for context.
Multi-hop RAG: Answer complex questions requiring multiple retrieval steps.
Interview tip: Know when to apply each pattern. Basic RAG is often sufficient.