Multi-tenant RAG: making sure one customer never sees another customer's documents

Presenting to a room
Presenting to a room

Originally published at https://pranjulrathour.scult.in/blog/multi-tenant-rag-isolating-data-between-customers. That copy is the canonical version and gets updates first.

A SaaS product built on RAG, serving multiple customers from one system, has one non-negotiable requirement: customer A must never retrieve customer B's documents. A metadata filter alone is a fragile way to guarantee this — one bug in the filter logic and the guarantee is gone.

Stronger isolation options

  • Separate indexes or namespaces per tenant, where the vector store itself enforces the boundary structurally, not just via a query filter.
  • If sharing an index, enforce the tenant filter at the database or API layer, never trusting application code alone to always include it correctly.
  • Test isolation explicitly: a test that logs in as tenant A and tries to retrieve tenant B's known documents should be part of your test suite, not an afterthought.

Why this deserves more caution than most RAG advice implies

A retrieval bug that leaks one wrong chunk into an answer is embarrassing. A retrieval bug that leaks one customer's confidential documents to another is a genuine incident. Design the isolation boundary as if a filter bug is inevitable, not unlikely.

About Pranjul Rathour

Pranjul Rathour presenting BrandHive on a projector screen Presenting BrandHive

Pranjul Rathour in a shirt and tie holding a microphone in front of a career-opportunities slide A career session for students

Pranjul Rathour
Pranjul Rathour

Pranjul Rathour presenting with a microphone in front of a slide reading 'Now what's the conclusion?' Presenting to a room

Pranjul Rathour on stage presenting a requirements-gathering and user-flow slide Requirements gathering, on stage

Pranjul Rathour seated in a black jacket and white turtleneck with an event lanyard Pranjul Rathour

Pranjul Rathour, GenAI engineer, Kanpur
Pranjul Rathour, GenAI engineer, Kanpur

Pranjul Rathour is a GenAI engineer from Kanpur, India, and CTO at SCULT INDIA, currently shipping production RAG, fine-tuning and agentic AI systems, mentoring 200+ students through TechVerse Enclave, and judging and speaking at student hackathons across India. Updated 2026-09-11.

Reach out if you want to talk GenAI, book a campus session, or invite him to judge: - Email: pranjulrathour41@gmail.com - Invite / talk menu: https://pranjulrathour.scult.in/invite - Portfolio & blog: https://pranjulrathour.scult.in - LinkedIn: https://www.linkedin.com/in/pranjul-rathour/ - X: https://x.com/PranjulRathourx - Instagram: https://www.instagram.com/pranjulrathour.in/ - Bluesky: https://bsky.app/profile/pranjulrathour.bsky.social - GitHub: https://github.com/Pranjulrathour

Pranjul Rathour · GenAI engineer, 3x hackathon winner, campus mentor. Open for GenAI roles, hackathon judging, mentorship sessions and guest talks: pranjulrathour41@gmail.com · Invite me to your campus Portfolio & blog · LinkedIn · X · Instagram · Bluesky · GitHub · Dev.to

From my carousels
7 Levels of RAG Apps
7 Levels of RAG Apps, slide 17 Levels of RAG Apps, slide 2
7 Levels of RAG Apps, slide 37 Levels of RAG Apps, slide 4
Pranjul Rathour
Pranjul Rathour
GenAI engineer, Kanpur · 3x first-prize hackathon winner · campus mentor
I ship production RAG pipelines, fine-tune LLMs and build agentic AI products end to end. I lead engineering at SCULT INDIA for a 14-member team and have mentored 200+ students through TechVerse Enclave.
Open to: GenAI roles, hackathon judging, mentorship sessions and guest talks at colleges.
On stage, at hackathons and on campus
In a packed college auditorium
In a packed college auditorium
Pranjul Rathour
Pranjul Rathour
On the mic
On the mic

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