Product design question

Design a permissions model so Glean never surfaces documents a user shouldn't see.

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What this question tests

Trust and safety product design for the single highest-stakes requirement in enterprise search: never leaking unauthorized content.

State the non-negotiable requirement: a permissions model must mirror the exact access rules of every connected source system, with zero tolerance for leakage.
Design real-time permission checks: at query time, filter results against the live access-control list from the source system rather than relying on a cached snapshot that could be stale.
Handle permission changes promptly: when access is revoked in a source system, that change must propagate to Glean's index quickly, not on a slow batch schedule.
Add a fail-safe default: if a permission check cannot be verified confidently, exclude the document rather than showing it, erring toward under-inclusion.
Add auditability: log every access decision so security teams can verify and investigate the permissions system's behavior.
Define success as zero permission-leak incidents in testing and production, verified through regular red-team style access audits.

Treats this as a zero-tolerance safety requirement, not a normal feature trade-off between coverage and precision.
Proposes real-time or near-real-time permission checks instead of relying on a potentially stale cached index.
Specifies a fail-safe default (exclude when uncertain) which is the correct posture for a security-critical system.
Adds auditability as a distinct requirement, since enterprise security teams will demand it before approving the product.
Proposes an ongoing red-team audit process rather than treating this as a one-time design decision.

Treating stale permission caches as an acceptable trade-off for search speed.
Not proposing an audit or verification mechanism for a security-critical system.

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