Optimize aggregate query mongoose - mongodb

Question

I'm trying to optimize a consult on mongoose. First my models go like this:
var TrackSchema = new Schema({
Car: {
type: Schema.ObjectId,
ref: 'Car'
},
Imei: {
type: String,
trim: true
},
Latitude: {
type: Number
},
Longitude: {
type: Number
}
});
var CarSchema = new Schema({
Basis: {
type: Schema.ObjectId,
ref: 'Basis'
},
Imei: {
type: String,
trim: true
}
});
var BasisSchema = new Schema({
Fence: {
type: Array,
}
});
What I want to do is to get the last registers from Tracks with distinct Imei from model Car. But also I need to get the Fence field from Basis that is associate with Car.
I alredy have the query, but I want to improve it because it take some time the get it.
Track.aggregate([
{
$group: {
_id: {
'Imei': '$Imei',
'Car': '$Car',
},
Longitude : { $last: '$Longitude' },
Latitude : { $last: '$Latitude' },
Fecha: { $last: '$CreatedDate'}
},
},
{
$lookup: {
from: 'cars',
localField: '_id.Car',
foreignField: '_id',
as: 'unit'
}
},
{
$unwind: '$unit'
},
{
$lookup: {
from: 'basis',
localField: 'unit.Basis',
foreignField: '_id',
as: 'geofence'
}
}
])
.exec(function(error, results){
});