NPSS cache consistency limits during policy revocation

Question

The Network Policy Security Service (NPSS) utilizes local caching at the enforcement points to minimize latency in high-frequency request environments. While this architecture optimizes performance, it relies on a Time-To-Live (TTL) mechanism for policy synchronization across distributed nodes.
A challenge arises when a critical policy update or revocation occurs in the central repository. Because the current implementation prioritizes periodic polling over immediate event-driven push notifications, there is a documented window where revoked permissions may still be honored by an edge node until the local cache expires or the next polling cycle completes.
What is the maximum guaranteed latency window between a central policy update and edge-node enforcement? Can the cache invalidation granularity be adjusted to support strict consistency without causing an unsustainable load on the policy management server?

Tasadduq Burney · Answer

The maximum guaranteed latency window between a central policy update and edge‑node enforcement is the sum of the cache time‑to‑live (TTL) and the interval between polling cycles. This bound is configuration‑dependent; there is no hard‑coded limit in the NPSS documentation.
Cache invalidation granularity can be tightened by reducing the TTL or increasing the polling frequency, which shortens the period during which revoked permissions may still be served. However, more frequent invalidation or shorter TTL raises request volume on the policy management server and can cause load spikes or cache thrashing if not monitored.
To determine the exact window for your environment you should:

Query the NPSS administration API or configuration file for the current TTL value (e.g., GET /api/v1/cache/ttl).
Query the same source for the polling interval (e.g., GET /api/v1/poll/interval).
Execute a controlled policy revocation in a test environment and record the timestamp when the central change occurs and the timestamp when an edge node logs the updated state.
Calculate the difference; it should not exceed TTL + poll interval, confirming the documented guarantee.

If the measured latency consistently approaches the TTL + poll interval limit, consider lowering the TTL or shortening the poll interval, but first verify that the policy server can sustain the increased request rate.
Please provide the current TTL and polling interval values for your NPSS deployment so a precise latency estimate can be given.

NPSS cache consistency limits during policy revocation

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