Question 993

The Nightly Sweep

An analytics job runs at 02:00 and reads about 10 million rows once each through the shared LRU cache. Every morning the interactive API's hit rate is near zero for the first hour and then recovers. What is happening?

A

The eviction sampler picks poor candidates when the request rate is low overnight, which is corrected by raising the number of keys sampled per eviction

B

A single-pass scan looks recent to LRU, so it evicts the API's working set; a frequency-aware or scan-resistant policy would survive it

C

The scan fragments the allocator's slabs, so usable capacity shrinks each night and only comes back when the process is restarted

D

The hot keys were written during the previous business day with TTLs that elapse overnight, so the morning misses are expiries rather than evictions