Challenge · intermediate · 25 min · Premium
Stale cache after a policy change
Northwind published a new coverage policy at nine and the assistant kept quoting the old one until lunch. Retrieval was fine. Find the layer that remembered, key it by what the answer depends on, and keep the hit rate.
Brief
- Customer
- Northwind Insurance (synthetic customer; every log, key and policy on this box is made up for the exercise)
- Situation
- Coverage policy CP-9 revision 2 went live at 09:00. Until 12:40 the assistant answered eye-exam questions with revision 1's text. The index was updated at 09:02 and returns revision 2. The prompt cache has a 15-minute TTL, which does not explain three and a half hours.
- Your role
- You are the FDE who owns the serving path. You have the cache config (bound to the live cache), the session records from the morning, and the console.
- Goal
- Name the layer that served the old policy, explain why the TTL did not save you, key the cache by the policy revision, and show the cache healthy with its hit rate intact.
Objectives
- 1.Name the layer that served the old policy (you commit to an answer)
- 2.Explain why a 15-minute TTL lasted three and a half hours (you commit to an answer)
- 3.Key the cache by the policy revision so a new revision is a new entry
- 4.Show the cache healthy with its hit rate still above 30%
Mission workspace
This mission is part of premium, with every challenge and incident in the lab. The brief above is the whole problem; the box, the hints and the debrief are what you unlock.
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