Thirty percent of your tail queries return zero results. Where do you start?

When a significant portion of tail queries returns zero results, the first step is to segment the query population to distinguish between different underlying issues that produce identical symptoms. A diagnostic test involves re-running the failing queries using a pure OR operator.

If the queries return documents under the OR condition, the defect lies in the query operator logic, and the appropriate fix is to implement soft matching. If the queries still return zero results even with an OR operator, the defect is a vocabulary mismatch, indicating that the index does not contain the terms being queried.