diff --git a/src/db_daterange.erl b/src/db_daterange.erl
new file mode 100644
index 0000000..4774487
--- /dev/null
+++ b/src/db_daterange.erl
@@ -0,0 +1,113 @@
+%%
+%% db_daterange.erl
+%% Kevin Lynx
+%% 07.10.2013
+%% To track the most recently hashes
+%%
+-module(db_daterange).
+-export([insert/2,
+		 lookup/3]).
+-export([start_link/1,
+		 stop/0]).
+-define(DBNAME, hash_date).
+-define(COLLNAME, hashes).
+-define(DATE_COL, date).
+-behaviour(gen_server).
+-export([init/1,
+         handle_call/3,
+         handle_cast/2,
+         handle_info/2,
+         terminate/2,
+         code_change/3]).
+-record(state, {startday, dbpool, counter}).
+-define(CHECK_BOUNDARY, 1000).
+-define(DEL_DAY_BEFORE_SECS, 5*24*60*60).
+
+% query by date (in seconds), build the index
+ensure_date_index(Conn) ->
+	Spec = {key, {?DATE_COL, 1}},
+	mongo:do(safe, master, Conn, ?DBNAME, fun() ->
+		mongo:ensure_index(?COLLNAME, Spec)
+	end).
+
+% '_id': Hash, date: DaySecs, reqs: RequestCount
+insert(Conn, Hash) when is_list(Hash) ->
+	DaySecs = time_util:now_day_seconds(),
+	BHash = list_to_binary(Hash),
+	Cmd = {findAndModify, ?COLLNAME, query, {'_id', BHash}, upsert, true,
+		update, {'$inc', {reqs, 1}, '$set', {?DATE_COL, DaySecs}}, fields, {'_id', 1}},
+	IRet = mongo:do(safe, master, Conn, ?DBNAME, fun() ->
+		mongo:command(Cmd)
+	end),
+	gen_server:cast(srv_name(), insert),
+	IRet.
+
+% [ListHash, ListHash]
+lookup(Conn, DaySecs, Count) ->
+	Sel = {'$query', {date, DaySecs}, '$orderby', {reqs, -1}},
+	List = mongo:do(safe, master, Conn, ?DBNAME, fun() ->
+		Cursor = mongo:find(?COLLNAME, Sel, {'_id', 1}, 0, Count), 
+		mongo_cursor:rest(Cursor)
+	end),
+	[decode_hash(Doc) || Doc <- List].
+
+decode_hash(Doc) ->
+	{ID} = bson:lookup('_id', Doc),
+	binary_to_list(ID).
+		
+% delete all oldest hashes 
+try_delete_oldest(Conn) ->
+	TodaySecs = time_util:now_day_seconds(),
+	DelDay = TodaySecs - ?DEL_DAY_BEFORE_SECS,
+	Sel = {date, {'$lte', DelDay}},
+	mongo:do(safe, master, Conn, ?DBNAME, fun() ->
+		mongo:delete(?COLLNAME, Sel)
+	end).
+
+%%%%
+start_link(DBPool) ->
+	gen_server:start_link({local, srv_name()}, ?MODULE, [DBPool], []).
+
+stop() ->
+	gen_server:cast(srv_name(), stop).
+
+srv_name() ->
+	?MODULE.
+
+init([Pool]) ->
+	Conn = mongo_pool:get(Pool),
+	ensure_date_index(Conn),
+	Today = time_util:now_day_seconds(),
+	{ok, #state{startday = Today, dbpool = Pool, counter = 0}}.
+
+terminate(_, State) ->
+    {ok, State}.
+
+code_change(_, _, State) ->
+    {ok, State}.
+
+% not care duplicated, check when there is more than 1 day
+handle_cast(insert, State) ->
+	#state{startday = StartDay, dbpool = Pool, counter = Count} = State,
+	NowDay = time_util:now_day_seconds(),
+	{NewCount, NewStart} = case Count > ?CHECK_BOUNDARY of
+		true when NowDay > StartDay ->
+			Conn = mongo_pool:get(Pool),
+			try_delete_oldest(Conn),
+			{0, NowDay};
+		true ->
+			{0, StartDay};
+		false ->
+			{Count + 1, StartDay}
+	end,
+	{noreply, State#state{startday = NewStart, counter = NewCount}};
+
+handle_cast(stop, State) ->
+	{stop, normal, State}.
+
+handle_call(_, _From, State) ->
+	{noreply, State}.
+
+handle_info(_, State) ->
+	{noreply, State}.
+
diff --git a/src/db_store_mongo.erl b/src/db_store_mongo.erl
index a3fc7b3..7b5c979 100644
--- a/src/db_store_mongo.erl
+++ b/src/db_store_mongo.erl
@@ -13,6 +13,7 @@
 		 inc_announce/2,
 		 exist/2,
 		 index/2,
+		 search_newest_top_by_date/3,
 		 search_announce_top/2,
 		 search_recently/2,
 		 search_newest_top/3,
@@ -57,6 +58,7 @@ search(Conn, Key) when is_list(Key) ->
 	end),
 	{decode_search(Ret), decode_search_stats(Ret)}.
 
+% deprecated
 search_announce_top(Conn, Count) ->
 	Sel = {'$query', {}, '$orderby', {announce, -1}},
 	List = mongo_do_slave(Conn, fun() ->
@@ -67,6 +69,7 @@ search_announce_top(Conn, Count) ->
 	end),
 	[decode_torrent_item(Item) || Item <- List].
  
+% deprecated
 % db.hashes.find({$query:{},$orderby:{created_at: 1}}).limit(10);
 search_recently(Conn, Count) ->
 	Sel = {'$query', {}, '$orderby', {created_at, -1}},
@@ -76,6 +79,7 @@ search_recently(Conn, Count) ->
 	end),
 	[decode_torrent_item(Item) || Item <- List].
 
+% deprecated
 search_newest_top(Conn, Count, DaySecs) ->	
 	Sel = {'$query', {created_at, {'$gt', DaySecs}}, '$orderby', {announce, -1}},
 	List = mongo_do_slave(Conn, fun() ->
@@ -84,6 +88,12 @@ search_newest_top(Conn, Count, DaySecs) ->
 	end),
 	[decode_torrent_item(Item) || Item <- List].
 
+% use hash_date to search, based on date index, so the search speed is very fast
+search_newest_top_by_date(Conn, Count, DaySecs) ->
+	Hashes = db_daterange:lookup(Conn, DaySecs, Count),
+	Infos = [index(Conn, Hash) || Hash <- Hashes],
+	lists:filter(fun(E) -> E /= {} end, Infos).
+
 index(Conn, Hash) when is_list(Hash) ->
 	Ret = mongo_do_slave(Conn, fun() ->
 		mongo:find_one(?COLLNAME, {'_id', list_to_binary(Hash)})
@@ -95,6 +105,7 @@ index(Conn, Hash) when is_list(Hash) ->
 
 insert(Conn, Hash, Name, Length, Files) when is_list(Hash) ->
 	NewDoc = create_torrent_desc(Conn, Hash, Name, Length, 1, Files),
+	db_daterange:insert(Conn, Hash),
 	mongo_do(Conn, fun() ->
 		% the doc may already exist because the other process has inserted before
 		Sel = {'_id', list_to_binary(Hash)},
@@ -115,14 +126,16 @@ inc_announce(Conn, Hash) when is_binary(Hash) ->
 	% damn, mongodb-erlang doesnot support update a field for an object,
 	% `findAndModify` works but it will change `announce' datatype to double
 	Cmd = {findAndModify, ?COLLNAME, query, {'_id', Hash}, 
-		update, {'$inc', {announce, 1}}, fields, {},
+		update, {'$inc', {announce, 1}}, fields, {'_id', 1}, % not specifed or {} will return whole object
 		new, false},
 	Ret = mongo_do(Conn, fun() ->
 		mongo:command(Cmd)
 	end),
 	case Ret of
 		{value, undefined, ok, 1.0} -> false;
-		{value, _Obj, lastErrorObject, {updatedExisting, true, n, 1}, ok, 1.0} -> true;
+		{value, _Obj, lastErrorObject, {updatedExisting, true, n, 1}, ok, 1.0} -> 
+			db_daterange:insert(Conn, binary_to_list(Hash)),
+			true;
 		_ -> false
 	end.
 
@@ -287,4 +300,8 @@ test_index(Hash) ->
 		index(Conn, Hash)
 	end).
 
+test_insertdate(Hash) ->
+	test_content(fun(Conn) ->
+		db_daterange:insert(Conn, Hash)
+	end).
 
diff --git a/src/hash_reader/hash_reader_sup.erl b/src/hash_reader/hash_reader_sup.erl
index e95d32f..9d84976 100644
--- a/src/hash_reader/hash_reader_sup.erl
+++ b/src/hash_reader/hash_reader_sup.erl
@@ -10,6 +10,7 @@
 		 start_dep_apps/0,
 		 start_standalone/3,
 		 start_standalone/1]).
+-define(DBPOOLNAME, mongodb_conn_pool_name).
 		 
 start_dep_apps() ->
 	code:add_path("deps/bson/ebin"),
@@ -37,13 +38,14 @@ start_standalone(IP, Port, Size) ->
 	Stats = {hash_reader_stats, {hash_reader_stats, start_link, [Size]}, permanent, 2000, worker, [hash_reader_stats]},
 	DownloadStats = {tor_download_stats, {tor_download_stats, start_link, []}, permanent, 2000, worker, [tor_download_stats]},
 	Log = {vlog, {vlog, start_link, ["log/hash_reader.log", 3]}, permanent, 2000, worker, [vlog]},
-	start_link(IP, Port, Size, [DownloadStats, Stats, Log]).
+	DBDateRange = {db_daterange, {db_daterange, start_link, [?DBPOOLNAME]}, permanent, 1000, worker, [db_daterange]},
+	start_link(IP, Port, Size, [Log, DBDateRange, DownloadStats, Stats]).
 
 start_link(IP, Port, Size) ->
 	start_link(IP, Port, Size, []).
 
 start_link(IP, Port, Size, OtherProcess) ->
-	PoolName = mongodb_conn_pool_name,
+	PoolName = ?DBPOOLNAME,
 	mongo_sup:start_pool(PoolName, 5, {IP, Port}),
 	% ensure index
 	Conn = mongo_pool:get(PoolName),
diff --git a/src/http_front/db_frontend.erl b/src/http_front/db_frontend.erl
index 6f1ce9f..48db28f 100644
--- a/src/http_front/db_frontend.erl
+++ b/src/http_front/db_frontend.erl
@@ -39,7 +39,7 @@ search_one(MagHash) ->
 find_day_top(_Conn, _DaySecs, 0) ->
 	[];
 find_day_top(Conn, DaySecs, Try) ->
-	case db_store_mongo:search_newest_top(Conn, 50, DaySecs) of
+	case db_store_mongo:search_newest_top_by_date(Conn, 50, DaySecs) of
 		[] ->
 			find_day_top(Conn, DaySecs - ?ONEDAY_SECS, Try - 1);
 		List ->
diff --git a/src/http_front/http_cache.erl b/src/http_front/http_cache.erl
index d603818..502866f 100644
--- a/src/http_front/http_cache.erl
+++ b/src/http_front/http_cache.erl
@@ -83,6 +83,14 @@ handle_info({enter_cache, Type, Time, Ret}, State) ->
 handle_info(_, State) ->
 	{noreply, State}.
 
+% for debug purpose
+query(top, State) ->
+	{State, do_update(top)};
+
+% for debug purpose
+query(stats, State) ->
+	{State, do_update(stats)};
+
 query(Type, State) ->
 	#state{cache = Cache} = State,
 	case gb_trees:is_defined(Type, Cache) of