Query Store Isn’t A Forensics Engine

Grant Fritchey shows that Query Store has a limited capability of finding “ill-behaving” queries at a point in time:

Here’s a great question I received: We had a problem at 9:02 AM this morning, but we’re not sure what happened. Can Query Store tell us?

My first blush response is, no. Not really. Query Store keeps aggregate performance metrics about the queries on the database where Query Store is enabled. Aggregation means that we can’t tell you what happened with an individual call at 9:02 AM…

Well, not entirely true.

Query Store isn’t a total solution for “Why was the system slow at XX:XX?” types of questions.  This does not diminish its value as long as you do not try to treat it as your only monitoring solution.