How would you design a multi-tenant RAG system?

For moderate tenant counts, use one index per tenant for strong isolation and independent scaling, accepting operational overhead. For high tenant counts, use a shared index with tenant ID in metadata and mandatory filtering on every query, using vector databases like Qdrant or Weaviate that support efficient filtered search. Enforce access control at the application layer before any query reaches the database. Consider per-tenant resource quotas to prevent noisy neighbors, and audit logging to satisfy compliance requirements.