indexing - Mongodb - increasing performance using compound index when pagination -

i'm newbie mongodb , need increasing performance queries using compound indexes.

i using pagination using "_id" field. query:

db.data.find( {"$or": [ { "cat": "5" }, {"cat": "6" } ] }, {"style": "3"},                {"area": "london"}, {"_id": {"$lt": 103}).sort( { "_id": 1 } ).limit(30) 

style , area can optional these possible.

db.data.find( {"$or": [ { "cat": "5" }, {"cat": "6" } ] },                 {"area": "london"}, {"_id": {"$lt": 103}).sort( { "_id": 1 } ).limit(30)  db.data.find( {"$or": [ { "cat": "5" }, {"cat": "6" } ] }, {"style": "3"},                {"_id": {"$lt": 103}).sort( { "_id": 1 } ).limit(30)  db.data.find( {"$or": [ { "cat": "5" }, {"cat": "6" } ] },                {"_id": {"$lt": 103}).sort( { "_id": 1 } ).limit(30) 

will these queries ok compound index, or need more additional index?

{ "cat": 1, "style": 1, "area": 1, "_id": 1 } 

edit

i'm not sure of these index efficient queries.

{ "cat": 1, "style": 1, "area": 1, "_id": 1 } or { "_id": 1, "cat": 1, "style": 1, "area": 1 } 

number of styles: 16

number of areas: 50

number of id: 10 million

use

{ "_id": 1, "cat": 1, "style": 1, "area": 1 } 

objectid has structure:

0 1 2 3   | 4 5 6   | 7 8 | 9 10 11 timestamp | machine | pid | increment 

because timestamp comes first in above structure, sort in insertion order.

when id came first in index, reduce looking objects.