Create a Qdrant payload index to speed up filtered search via PUT /collections/{collection_name}/index

Documented steps

1. Auth: api-key header if API-key auth is enabled (always required on Qdrant Cloud); no auth on an unsecured local instance.
2. Pick the payload field and schema type: keyword, integer, float, bool (v1.4.0+), geo, datetime (v1.8.0+), text (full-text), or uuid (v1.11.0+)
3. Create the index: curl -X PUT http://localhost:6333/collections/my_collection/index -H 'Content-Type: application/json' -d '{"field_name": "category", "field_schema": "keyword"}'
4. Create payload indexes before bulk-ingesting data where possible — Qdrant builds filter-aware HNSW edges as points are added
5. Index only the fields you actually filter on — each index adds memory/disk overhead
6. Official docs: https://qdrant.tech/documentation/manage-data/indexing/