db={"greetsthings":[{"_id":ObjectId("5d24e6e5e8b6b11536a8519b"),"message":"hello","meta":{"info":"friendly score 923","things":"cat bat dragon"}},{"_id":ObjectId("5d24e6e5e8b6b11536a8519c"),"message":"hello","meta":{"info":"confused score 622","things":"cat monkey dragon"}}]}

db.greetsthings.aggregate([{$match:{$expr:{$and:[{$eq:["$message","hello"]},{$gt:[{$indexOfCP:["$meta.things","monkey"]},-1]}]}}}])