How does Qdrant handle filtering during vector search?

Qdrant integrates payload filtering directly into HNSW traversal, a technique called filterable HNSW. Instead of filtering before or after search, Qdrant considers the filter while walking the graph, maintaining recall even under highly selective filters. To make this efficient, payload fields used in filters should have payload indexes created on them, which Qdrant uses to check filter matches without loading full payloads. This design makes Qdrant particularly strong when queries combine semantic similarity with structured constraints.