Reconcile RAG Document Expiry, Chat History, and Cold Audits

Design the data lifecycle and history store for a document-grounded conversation system with these reported requirements:

• Uploaded documents and vector indexes expire after 24 hours and must be physically deleted with zero residual data.
• Conversation history remains available for 7 days.
• The user's sidebar should load past conversation history in less than 10 milliseconds.
• An enterprise may additionally request read-only conversation auditing for months or years.

Explain how these requirements interact, which ones need clarification, and how the system behaves when a user opens a four-day-old conversation whose documents have expired.

Constraints & Assumptions

• A retained answer may itself contain information copied or derived from an uploaded document.
• The selected vector store may lack native per-record TTL; do not assume that deleting a primary row removes every replica, backup, cache, or derived artifact instantly.
• The source does not define the start of the 24-hour clock, the measurement boundary of the 10-millisecond target, or whether “all history” means conversation summaries or full transcripts.
• Long-term audit retention must be reconciled with the shorter deletion rules; it is not an automatic exception.

Clarifying Questions to Ask

• Is expiry measured from upload, session creation, or last activity, and does it cover extracted text, embeddings, answers, logs, and backups?
• Is exact physical erasure required at the deadline, or is access revocation at the deadline followed by a bounded verified deletion process acceptable?
• May a day-four conversation remain readable but lose document-grounded follow-up capability?
• Which audit fields may be retained without contradicting document or transcript deletion obligations?

Part 1 — Enforce Expiry Across Stores

Describe ownership, expiry metadata, access gating, deletion scheduling, vector cleanup, and evidence that the deletion process completed.

What This Part Should Cover

• An inventory of raw and derived copies with a common lifecycle identity.
• Query-time expiry enforcement and physical-reclamation mechanisms appropriate to each store.
• Retryable deletion and honest treatment of replicas, backups, and exact-deadline feasibility.

Part 2 — Serve Historical Conversations

Design conversation-list queries and the expired-document product state. Explain how the sidebar target can be approached without reading every full transcript.

What This Part Should Cover

• Tenant/user-scoped time indexes, bounded projections, and pagination where permitted.
• Separate availability of transcript history and document-grounded querying.
• Cache expiry and authorization consistent with retention rules.

Part 3 — Reconcile Long-Term Audit

Describe a cold audit path that does not slow the online database, and identify the policy conflict that must be resolved before archiving sensitive content.

What This Part Should Cover

• Explicit permitted audit scope and retention, not a hidden copy of supposedly deleted content.
• Immutable/read-only storage controls, lifecycle rules, and offline query paths.
• Verification that archive and backup behavior matches the agreed deletion semantics.