Thanks, dunno about the “target” response range.
I checked one other endpoint that is simpler and its responses are around 120ms.
This API I am talking about is used in iOS and Android mobile apps - I should have specified this in the first post. So it is send as JSON and parsed in the app.
Since the server is in Germany and I have a lot of users in the US and Asia I think improving the response rate could perhaps be more noticeable to those users.
I am not using any pooling or similar stuff. I read a bit yesterday (Improve Serialization Performance in Django Rest Framework | Haki Benita) and so far tried just the read_only_fields tip on some serializers - but I dont have data yet to know how much this helped.
As for the queries - the ones for this endpoint are based on my previous post (How to order_by ForeignKey that matches query?) so there is lot of subqueries going on.