Question 1004

Outgrew Its Sizing

A Bloom filter was sized for 1 million keys at a 1 percent false positive rate and now holds 8 million. The penetration guard has become useless: almost every request is forwarded to the database. What is the correct response?

A

Increase k on the existing array, so each probe checks more positions and the chance of an accidental match falls back toward 1 percent

B

The array is nearly saturated so the false positive rate has climbed steeply; rebuild at the right size, since it cannot be resized in place

C

The hash seeds have degraded as the array filled, and rotating them redistributes the set bits so the original error rate returns

D

False negatives now dominate, so real keys are being reported missing and their lookups are skipped entirely before they ever reach the database