Mongo db query time more than expected - mongodb

Question

I am running standalone mongodb server with version 3.4. I am using following query on my collection which contains around 1.8 million document out of which around 1 million document are in "ARCHIVED" status.
db.tender_listing.find({ "tender_id" : { "$gt" : "d"} , "workflow_status" : { "$in" : [ "ARCHIVED"]}}).limit(4000).sort({tender_id:1}).hint({workflow_status:1, tender_id:1}).explain('executionStats')
Each query stage has executionTimeMillisEstimate of not more than 100ms but the total executionTimeMillis is 30992.
For what operation query is taking this much extra time? Also how can I optimise same?
Following is the output
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "ofbTenders.tender_listing",
"indexFilterSet" : false,
"parsedQuery" : {
"$and" : [
{
"workflow_status" : {
"$eq" : "ARCHIVED"
}
},
{
"tender_id" : {
"$gt" : "d"
}
}
]
},
"winningPlan" : {
"stage" : "LIMIT",
"limitAmount" : 4000,
"inputStage" : {
"stage" : "FETCH",
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"workflow_status" : 1,
"tender_id" : 1
},
"indexName" : "workflow_status_1_tender_id_1",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1,
"direction" : "forward",
"indexBounds" : {
"workflow_status" : [
"[\"ARCHIVED\", \"ARCHIVED\"]"
],
"tender_id" : [
"(\"d\", {})"
]
}
}
}
},
"rejectedPlans" : [ ]
},
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 4000,
"executionTimeMillis" : 30992,
"totalKeysExamined" : 4000,
"totalDocsExamined" : 4000,
"executionStages" : {
"stage" : "LIMIT",
"nReturned" : 4000,
"executionTimeMillisEstimate" : 90,
"works" : 6129,
"advanced" : 4000,
"needTime" : 0,
"needYield" : 2128,
"saveState" : 2128,
"restoreState" : 2128,
"isEOF" : 1,
"invalidates" : 0,
"limitAmount" : 4000,
"inputStage" : {
"stage" : "FETCH",
"nReturned" : 4000,
"executionTimeMillisEstimate" : 80,
"works" : 6128,
"advanced" : 4000,
"needTime" : 0,
"needYield" : 2128,
"saveState" : 2128,
"restoreState" : 2128,
"isEOF" : 0,
"invalidates" : 0,
"docsExamined" : 4000,
"alreadyHasObj" : 0,
"inputStage" : {
"stage" : "IXSCAN",
"nReturned" : 4000,
"executionTimeMillisEstimate" : 10,
"works" : 4000,
"advanced" : 4000,
"needTime" : 0,
"needYield" : 0,
"saveState" : 2128,
"restoreState" : 2128,
"isEOF" : 0,
"invalidates" : 0,
"keyPattern" : {
"workflow_status" : 1,
"tender_id" : 1
},
"indexName" : "workflow_status_1_tender_id_1",
"isMultiKey" : false,
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 1,
"direction" : "forward",
"indexBounds" : {
"workflow_status" : [
"[\"ARCHIVED\", \"ARCHIVED\"]"
],
"tender_id" : [
"(\"d\", {})"
]
},
"keysExamined" : 4000,
"seeks" : 1,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0
}
}
}
},
"serverInfo" : {
"host" : "ofb59-Latitude-3450",
"port" : 27017,
"version" : "3.4.4",
"gitVersion" : "888390515874a9debd1b6c5d36559ca86b44babd"
},
"ok" : 1
}

Answer 1

I am not sure but you can try below option.
1) instead of using $in for workflow you can give directly "workflow_status" : "ARCHIVED"
2) change order of fields in find first workflow status and then tender_id.
3) run query execution plan without hint. Let MongoDB decide which index to use.