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. ```hint Follow one paragraph into every copy Deleting the uploaded file does not remove a quoted paragraph from a chat answer, an extraction cache, or an archived log. Decide which copies the deletion requirement covers. ``` ### What a Strong Answer Covers - Technically enforceable lifecycle boundaries and explicit unresolved conflicts. - A usable history experience after document expiry. - Bounded fast history reads and a separately governed audit path. ### Follow-up Questions - Why is a database TTL index alone insufficient to prove exact-time physical deletion? - How would you handle a failed vector-delete request at the expiry boundary? - Can encryption-key destruction satisfy the stated requirement if it specifically demands physical byte removal?