Short answer: for an ask-your-docs feature in a multi-tenant SaaS help center, start with embeddings over document chunks, retain keyword search for exact identifiers, and add reranking only when retrieval evaluation shows that the first-stage ordering is weak. The architecture is simple: ingest tenant-scoped chunks, embed them, store the vectors in a managed index, retrieve a small candidate set, and give only those matches to the answer model. The important marketplace constraint is less gl...