Visibility into persistent query progress

Looking at the metrics I see that one can use consumer-messages-per-sec on a persistent query to view overall processing speed wrt. to query inputs.

Is there any way to get something like “last processed record timestamp”? We need to answer the question “how far behind is our ksqlDB query in processing the input”.

NOTE: the query takes loads of input from 2 topics and only outputs very seldom (when something is wrong between them)

You can monitor the lag of the query in number of offsets (not based on time), but it should be a good enough proxy?