Mongo Remove records in a huge collection - mongodb

Question

I have a huge collection (1000 Million) and I would like to search and remove the records older than a timestamp.
I have an index created on the field lastUpdatedTime
db.MyCol.remove({"lastUpdatedTime" : {$lt: ISODate("2016-10-06 00:00:00 AM") }})
The above remove query timeouts and I modified to use BulkOperation as well.
Failed execution of command 'delete' with id 4334 on connection
'connectionId{localValue:13, serverValue:22}' to server 'XXXXX:27017'
with exception 'com.mongodb.MongoSocketReadTimeoutException: Timeout
while receiving message'
I understand mongo doesn't support limit in remove yet. So, I am implementing something like below
//Read 10K records
BasicDBObject query = new BasicDBObject();
query.append("lastUpdatedTime",
new BasicDBObject("$lte", new Timestamp(cal.getTimeInMillis())));
DBCursor cursorDocBuilder = myCol.find(query).limit(10000);
// Get Ids
BasicDBList inList = new BasicDBList();
while (cursorDocBuilder.hasNext())
{
inList.add(cursorDocBuilder.next().get("_id"));
}
//construct In clause
BasicDBObject deleteQuery = new BasicDBObject();
deleteQuery.put("_id", new BasicDBObject(MongoOps.$IN, inList));
WriteResult result =myCol.remove(deleteQuery);
What would be a good number to remove using $IN clause?
Will it better to fire multiple remove statements instead a big one with many IN clause?
I think this is a everyday situation to delete the top N records in a database. Is there a better way of achieving this?
P.S : I can do multiple threads to clean up. I don't want to throttle the database as I anticipate high read /write operations to the same collection.
Adding the explain() for fetching 1000 records
{
"queryPlanner" : {
"plannerVersion" : 1,
"namespace" : "XXX",
"indexFilterSet" : false,
"parsedQuery" : {
"lastUpdatedTime" : {
"$lt" : ISODate("2016-10-06T00:00:00Z")
}
},
"winningPlan" : {
"stage" : "LIMIT",
"limitAmount" : 1000,
"inputStage" : {
"stage" : "FETCH",
"inputStage" : {
"stage" : "IXSCAN",
"keyPattern" : {
"lastUpdatedTime" : 1
},
"indexName" : "lastUpdatedTime_1",
"isMultiKey" : false,
"multiKeyPaths" : {
"lastUpdatedTime" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"lastUpdatedTime" : [
"(true, new Date(1475712000000))"
]
}
}
}
},
"rejectedPlans" : [ ]
},
"executionStats" : {
"executionSuccess" : true,
"nReturned" : 1000,
"executionTimeMillis" : 200,
"totalKeysExamined" : 1000,
"totalDocsExamined" : 1000,
"executionStages" : {
"stage" : "LIMIT",
"nReturned" : 1000,
"executionTimeMillisEstimate" : 201,
"works" : 1001,
"advanced" : 1000,
"needTime" : 0,
"needYield" : 0,
"saveState" : 10,
"restoreState" : 10,
"isEOF" : 1,
"invalidates" : 0,
"limitAmount" : 1000,
"inputStage" : {
"stage" : "FETCH",
"nReturned" : 1000,
"executionTimeMillisEstimate" : 201,
"works" : 1000,
"advanced" : 1000,
"needTime" : 0,
"needYield" : 0,
"saveState" : 10,
"restoreState" : 10,
"isEOF" : 0,
"invalidates" : 0,
"docsExamined" : 1000,
"alreadyHasObj" : 0,
"inputStage" : {
"stage" : "IXSCAN",
"nReturned" : 1000,
"executionTimeMillisEstimate" : 0,
"works" : 1000,
"advanced" : 1000,
"needTime" : 0,
"needYield" : 0,
"saveState" : 10,
"restoreState" : 10,
"isEOF" : 0,
"invalidates" : 0,
"keyPattern" : {
"lastUpdatedTime" : 1
},
"indexName" : "lastUpdatedTime_1",
"isMultiKey" : false,
"multiKeyPaths" : {
"lastUpdatedTime" : [ ]
},
"isUnique" : false,
"isSparse" : false,
"isPartial" : false,
"indexVersion" : 2,
"direction" : "forward",
"indexBounds" : {
"lastUpdatedTime" : [
"(true, new Date(1475712000000))"
]
},
"keysExamined" : 1000,
"seeks" : 1,
"dupsTested" : 0,
"dupsDropped" : 0,
"seenInvalidated" : 0
}
}
}
}