Mongodb query execution take too much time - mongodb

Question

Iam working on the Go project and I am using mongodb to store my data. But suddenly the mongodb query execution took too much time to get data.
I have a collection named "cars" with around 25000 documents and each document containing around 200 fields (4.385KB). I have an aggregate query like this:
db.cars.aggregate([
{
$lookup:
{
from: "users",
localField: "uid",
foreignField: "_id",
as: "customer_info"
}
},{
$unwind: "$customer_info"
},{
$lookup:
{
from: "user_addresses",
localField: "uid",
foreignField: "_id",
as: "address"
}
},{
$unwind: "$address"
},{
$lookup:
{
from: "models",
localField: "_id",
foreignField: "car_id",
as: "model_info"
}
},{
$match:{
purchased_on:{$gt:1538392491},
status:{$in:[1,2,3,4]},
"customer_info.status":{$ne:9},
"model_info.status":{$ne:9},
}
},{
$sort:{
arrival_time:1
}
},{
$skip:0
},{
$limit:5
}
])
My document structure is like: https://drive.google.com/file/d/1hM-lPwvE45_213rQDYaYuYYbt3LRTgF0/view.
Now, If run this query with out indexing then it take around 10 mins to load the data. Can anyone suggest me how can I reduce its execution time ?

Answer 1

There are many things to do to optimize your query. What I would try :
As Anthony Winzlet said in comments, use as possible $match stage as first stage. This way, you can reduce number of documents passed to the following stages, and use indexes.
Assuming you use at least 3.6 mongo version, change your lookup stages using the 'let/pipeline' syntax (see here). This way, you can integrate your 'external filters' ( "customer_info.status":{$ne:9}, "model_info.status":{$ne:9} ) in a $match stage in your lookups pipeline. With indexes on right fields / collections, you will gain some time / memory in your $lookup stages.
Do your unwind stages as late as possible, to restrict number of documents passed to the following stages.
It's important to understand how works aggregation pipeline : each stage receive data, do its stuff, and pass data to next stage. So the less data is passed to the pipeline, the faster will be your query.