Hi @DrEdWilliams - I’m still coming up to speed on some of this, but at first glance, the syntax of your query looks correct. I suspect there might be some kind of data type mismatch issue going on - is @timestamp configured as a date type in your index mapping? OpenSearch will do its best to detect the appropriate mapping if you haven’t explicitly provided one, but it’s not always perfect at it.
I’ll see if I can consult some subject matter experts for you.
Nate