[{"subject":"Hello there","events":[{"status":"opened","date":"2020-01-02 17:35:31.229Z"},{"status":"clicked","date":"2020-01-01 17:35:31.229Z"}]},{"subject":"Hello there","events":[{"status":"opened","date":"2020-01-01 17:35:31.229Z"},{"status":"clicked","date":"2020-01-02 17:35:31.229Z"}]}]

db.collection.aggregate([{$addFields:{lastevent:{$filter:{input:"$events",as:"element",cond:{$eq:["$$element.date",{$max:"$events.date"}]}}}}},{$match:{"lastevent.status":"opened"}}])