Happy New Year! I’ve written up my issue here, any help is greatly appreciated.
Happy New Year to you @Matthew_77253.
I don’t quite follow what you’re asking. Can you expand a bit more before I look at the Explain and the Queries? And are you saying that no index is being used at all in the aggregation pipeline?
You also need to give some indication as to the approx number of records in the collection, the full definition of the index or indexes including the direction of the sort on each field, expected number of records returned etc.
In any case, a covered query will always perform better than any other type of query.