.tip

A search that finds nothing returns 200 in 20 milliseconds, so on a dashboard it looks like your healthiest request. The person behind it retyped the query twice and left. Log the normalized query with the hit count on every search, then read the zero-hit ones once a week.

log.info("search", { query: q.trim().toLowerCase(), hits: results.length });

The list is short, and it is the same three things: synonyms the index never learned, a product people spell another way, pages nobody wrote.