You store simple counts, and whenever a particular type of query is made you increment the relevant count(s). Exactly. As a plus, precise accuracy isn't neces

You store simple counts, and whenever a particular type of query is made you increment the relevant count(s). Exactly. As a plus, precise accuracy isn't necessary here, no-one's going to care if you report 39,893 instead of 19,898 queries per minute. Simple counters + regular reset to zero would do the job well enough.