An application needs to filter results to only documents in a specific category before applying vector similarity search. What is this pattern called?

1. A Post-filtering
2. ✓ B Pre-filtering (filtered ANN) (correct answer)
3. C Hybrid search
4. D Metadata retrieval

Shortcut: Pre-filtering applies a WHERE clause predicate before or during ANN search. pgvector with HNSW supports filtered search: SELECT ... WHERE category = 'X' ORDER BY embedding <=> $1 LIMIT 10.