Filter nested populated array - node.js

Question

Lets say I have a classroom that look like this:
{
courseName: String,
teacher: ObjectId,
students: [{type: ObjectId, ref: 'Student'}]
}
and the "Student" schema looks like this:
{
personalInfo: PersonalInfo,
proffesionalInfo: {type: ObjectId, ref: 'ProffesionalInfo'}
}
and the "ProffesionalInfo" schema looks like this:
{
allgrades: [Number],
averageGrade: Number,
...
...
}
I have the classroom _id and I want to get only the students that their average is lower than 90.
The way I am doing it now is like this:
Classroom.findOne({ _id })
.populate("teacher", "_id name")
.populate({
path: 'ridesstudents',
select: 'proffesionalInfo',
populate: [
{
path: "proffesionalInfo",
select: "allgrades averageGrade"
}
]
})
.then(classroom => {
classroom.students = classroom.students.filter(student => student.proffesionalInfo.averageGrade < 90);
resolve(user);
})
.catch(err => reject(err));
As you can see I am filtering after bringing all student.
In case I have 10 million student and only 2 with grade less than 90 It is "not good" approach.
How can I filter the students within the query and not bringing all of them and then filtering??
side note - the data above is only an exaple which target is to bring the general idea. dont get into details.

Answer 1

Try using aggregate:
let classroom = Classroom.aggregate([
{ $match: { _id: classroomId } },
{ $lookup: {
from: "students",
localField: "_id",
foreignField: "students",
pipeline:[
{ $lookup: {
from: "professionalInfo",
localField: "_id",
foreignField: "proffesionalInfo",
as:"professionalInfo"
}},
{ $match: {$lte: ["professionalInfo.averageGrade",90]}}
]
as: "students"
}}])