//create a simple document that has an array of embedded doc, like this:
var doc = {
    "annotationList": [
        {
            "meta": {
                "league": "league_value1",
				"class": "class_value1"
            }
        },
        {
            "meta": {
                "league": "league_value1",
				"class": "class_value1"
            }
        }
    ]
}

//save doc to the collection
db.testCollection.save(doc);


//build compound index using 2 multikey field
db.testCollection.ensureIndex({"annotationList.meta.league": 1, "annotationList.meta.league": 1});

db.testCollection.explain("executionStats").count({
	
	"annotationList": {
		"$elemMatch": {
			"meta.league": "league_value1"
		}
	}
	
});

cursor = db.testCollection.explain("executionStats").count({
	
	"annotationList.meta.league": "league_value1"

});