Query Store was designed to be clever, and to minimize its impact on your performance. Query Store only flushes its data from memory to disk periodically. You get to control this by setting the data flush interval in the Query Store settings for a database. (Read more about this in Microsoft Documentation here.)
The default value for Query Store data flush is 15 minutes. That means that in the case of a crash, you might lose up to around 15 minutes of activity.
Even if you’ve lowered this, you might want to make sure that a backup contains the very latest activity, particularly if you’re taking the backup to get Query Store data for someone to look at.
Read the whole thing.