Compound index for sort and range

hi,
i want to create a compound index for sort and range filter,
i dont know why its doing a seperate filter and not using the compound index for the range filter.

here is my data:

{ 
    "_id" : ObjectId("6080a5c299aecc30a333dfc7"), 
    "name" : "Shakir", 
    "location" : "Ottawa", 
    "region" : "AMER", 
    "joined" : 2015
}
{ 
    "_id" : ObjectId("6080a5c299aecc30a333dfc8"), 
    "name" : "Chris", 
    "location" : "Austin", 
    "region" : "AMER", 
    "joined" : 2016
}
{ 
    "_id" : ObjectId("6080a5c299aecc30a333dfc9"), 
    "name" : "III", 
    "location" : "Sydney", 
    "region" : "APAC", 
    "joined" : 2016
}
{ 
    "_id" : ObjectId("6080a5c299aecc30a333dfca"), 
    "name" : "Miguel", 
    "location" : "Barcelona", 
    "region" : "EMEA", 
    "joined" : 2017
}
{ 
    "_id" : ObjectId("6080a5c299aecc30a333dfcb"), 
    "name" : "Alex", 
    "location" : "Toronto", 
    "region" : "AMER", 
    "joined" : 2018
}

and i created this index:
db.getCollection("region").createIndex({ "region" : 1, "joined" : 1})

this is my query:
db.getCollection("region").find({ joined: { $gt: 2015 } }).sort({ region: 1, })

here is my winning plan:

"winningPlan" : { 
        "stage" : "FETCH", 
        "filter" : { 
            "joined" : { 
                "$gt" : 2015.0
            }
        }, 
        "inputStage" : { 
            "stage" : "IXSCAN", 
            "keyPattern" : { 
                "region" : 1.0, 
                "joined" : 1.0
            }, 
            "indexName" : "region_1_joined_1", 
            "isMultiKey" : false, 
            "multiKeyPaths" : { 
                "region" : [

                ], 
                "joined" : [

                ]
            }, 
            "isUnique" : false, 
            "isSparse" : false, 
            "isPartial" : false, 
            "indexVersion" : 2, 
            "direction" : "forward", 
            "indexBounds" : { 
                "region" : [
                    "[MinKey, MaxKey]"
                ], 
                "joined" : [
                    "[MinKey, MaxKey]"
                ]
            }
        }
    }

thanks

Hi @Landau_Yoel, and welcome to the community,
I quote from Sort and Non-prefix Subset of an Index

If the query does not specify an equality condition on an index prefix that precedes or overlaps with the sort specification, the operation will not efficiently use the index.

which means, regardless of your index, mongodb will do a SORT or a FETCH+filter.