MongoDB first query taking time in Java Spring Boot application - mongodb

Question

I have following peace of java spring mongoDB code:
startTime = System.currentTimeMillis();
AggregationResults<MyClass> list = mongoTemplate.aggregate(Aggregation.newAggregation(operations),
"Post", MyClass.class);
System.out.println("Time taken for query execution -> "
+ (System.currentTimeMillis() - startTime));
when i am testing this code using jmeter, first execution shows:
Time taken for query execution -> 3275 ('list' has 16 records)
On 2nd and henceforth request its liks
Time taken for query execution -> 355 ('list' has 16 records)
Time difference is huge. How can I improve it in first call ?
When I do Aggregation.newAggregation(operations).toString() I am getting following query output. Running the folliwng aggregation query on shell command always take around .350sec.
{
"aggregate": "__collection__",
"pipeline": [
{
"$match": {
"$and": [
{
"postType": "AUTOMATIC"
}
]
}
},
{
"$project": {
"orders.id": 1,
"postedTotals": 1
}
},
{
"$unwind": "$orders"
},
{
"$group": {
"_id": "$orders.userId",
"ae": {
"$addToSet": "$orders.userId"
}
}
},
{
"$sort": {
"ae": 1
}
}
]
}
.explain().aggregate( shows following:
/* 1 */
{
"stages" : [
{
"$cursor" : {
"query" : {
"$and" : [
{
"postType" : "AUTOMATIC"
}
]
},
"fields" : {
"headerPostedTotals" : 1,
"orders.UserId" : 1,
"_id" : 1
},
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "post",
"indexFilterSet" : false,
"parsedQuery" : {
"postType" : {
"$eq" : "AUTOMATIC"
}
},
"winningPlan" : {
"stage" : "FETCH",
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"postType" : 1,
"orders.UserId" : 1,
"orders.flightStartDateForQuery" : 1,
"orders.flightEndDateForQuery" : 1,
"postRunDate" : -1
},
"indexName" : "default_filter_index",
"isMultiKey" : true,
"multiKeyPaths" : {
"postType" : [],
"orders.UserId" : [
"orders"
],
"orders.flightStartDateForQuery" : [
"orders"
],
"orders.flightEndDateForQuery" : [
"orders"
],
"postRunDate" : []
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"postType" : [
"[\"AUTOMATIC\", \"AUTOMATIC\"]"
],
"orders.UserId" : [
"[MinKey, MaxKey]"
],
"orders.flightStartDateForQuery" : [
"[MinKey, MaxKey]"
],
"orders.flightEndDateForQuery" : [
"[MinKey, MaxKey]"
],
"postRunDate" : [
"[MaxKey, MinKey]"
]
}
}
},
"rejectedPlans" : []
}
}
},
{
"$project" : {
"_id" : true,
"headerPostedTotals" : true,
"orders" : {
"UserId" : true
}
}
},
{
"$unwind" : {
"path" : "$orders"
}
},
{
"$group" : {
"_id" : "$orders.UserId",
"aes" : {
"$addToSet" : "$orders.UserId"
}
}
},
{
"$sort" : {
"sortKey" : {
"aes" : 1
}
}
}
],
"ok" : 1.0
}