diff --git a/apps/emqx_replay/src/emqx_replay_local_store.erl b/apps/emqx_replay/src/emqx_replay_local_store.erl
index 35a31e65c..77f0b2924 100644
--- a/apps/emqx_replay/src/emqx_replay_local_store.erl
+++ b/apps/emqx_replay/src/emqx_replay_local_store.erl
@@ -61,6 +61,10 @@
 }).
 
 -record(it, {
+    zone :: emqx_types:zone(),
+    gen :: gen_id(),
+    filter :: emqx_topic:words(),
+    start_time :: emqx_replay:time(),
     module :: module(),
     data :: term()
 }).
@@ -95,31 +99,36 @@ create_generation(Zone, Since, Config = {_Module, _Options}) ->
 -spec store(emqx_types:zone(), emqx_guid:guid(), emqx_replay:time(), emqx_replay:topic(), binary()) ->
     ok | {error, _TODO}.
 store(Zone, GUID, Time, Topic, Msg) ->
-    #{module := Mod, data := Data} = meta_lookup_gen(Zone, Time),
+    {_GenId, #{module := Mod, data := Data}} = meta_lookup_gen(Zone, Time),
     Mod:store(Data, GUID, Time, Topic, Msg).
 
 -spec make_iterator(emqx_types:zone(), emqx_topic:words(), emqx_replay:time()) ->
-    {ok, _TODO} | {error, _TODO}.
+    {ok, iterator()} | {error, _TODO}.
 make_iterator(Zone, TopicFilter, StartTime) ->
-    %% TODO: this is not supposed to work like this. Just a mock-up
-    #{module := Mod, data := Data} = meta_lookup_gen(Zone, StartTime),
-    case Mod:make_iterator(Data, TopicFilter, StartTime) of
-        {ok, It} ->
-            {ok, #it{
-                module = Mod,
-                data = It
-            }};
-        Err ->
-            Err
-    end.
+    {GenId, Gen} = meta_lookup_gen(Zone, StartTime),
+    open_iterator(Gen, #it{
+        zone = Zone,
+        gen = GenId,
+        filter = TopicFilter,
+        start_time = StartTime
+    }).
 
 -spec next(iterator()) -> {value, binary(), iterator()} | none | {error, closed}.
-next(#it{module = Mod, data = It0}) ->
-    case Mod:next(It0) of
-        {value, Val, It} ->
-            {value, Val, #it{module = Mod, data = It}};
-        Other ->
-            Other
+next(It = #it{module = Mod, data = ItData}) ->
+    case Mod:next(ItData) of
+        {value, Val, ItDataNext} ->
+            {value, Val, It#it{data = ItDataNext}};
+        {error, _} = Error ->
+            Error;
+        none ->
+            case open_next_iterator(It) of
+                {ok, ItNext} ->
+                    next(ItNext);
+                {error, _} = Error ->
+                    Error;
+                none ->
+                    none
+            end
     end.
 
 %%================================================================================
@@ -232,6 +241,24 @@ open_gen(
     DB = Mod:open(Zone, DBHandle, GenId, CFs, Data),
     Gen#{data := DB}.
 
+-spec open_next_iterator(iterator()) -> {ok, iterator()} | {error, _Reason} | none.
+open_next_iterator(It = #it{zone = Zone, gen = GenId}) ->
+    open_next_iterator(meta_get_gen(Zone, GenId + 1), It#it{gen = GenId + 1}).
+
+open_next_iterator(undefined, _It) ->
+    none;
+open_next_iterator(Gen = #{}, It) ->
+    open_iterator(Gen, It).
+
+-spec open_iterator(generation(), iterator()) -> {ok, iterator()} | {error, _Reason}.
+open_iterator(#{module := Mod, data := Data}, It = #it{}) ->
+    case Mod:make_iterator(Data, It#it.filter, It#it.start_time) of
+        {ok, ItData} ->
+            {ok, It#it{module = Mod, data = ItData}};
+        Err ->
+            Err
+    end.
+
 %% Functions for dealing with the metadata stored persistently in rocksdb
 
 -define(CURRENT_GEN, <<"current">>).
@@ -282,31 +309,42 @@ meta_register_gen(Zone, GenId, Gen) ->
     ok = meta_put(Zone, GenId, [Gen | Gs]),
     ok = meta_put(Zone, current, GenId).
 
--spec meta_lookup_gen(emqx_types:zone(), emqx_replay:time()) -> generation().
+-spec meta_lookup_gen(emqx_types:zone(), emqx_replay:time()) -> {gen_id(), generation()}.
 meta_lookup_gen(Zone, Time) ->
     % TODO
     % Is cheaper persistent term GC on update here worth extra lookup? I'm leaning
     % towards a "no".
-    GenId = meta_lookup(Zone, current),
-    Gens = meta_lookup(Zone, GenId),
-    [Gen | _Older] = lists:dropwhile(fun(#{since := Since}) -> Since > Time end, Gens),
-    Gen.
+    Current = meta_lookup(Zone, current),
+    Gens = meta_lookup(Zone, Current),
+    find_gen(Time, Current, Gens).
+
+find_gen(Time, GenId, [Gen = #{since := Since} | _]) when Time >= Since ->
+    {GenId, Gen};
+find_gen(Time, GenId, [_Gen | Rest]) ->
+    find_gen(Time, GenId - 1, Rest).
+
+-spec meta_get_gen(emqx_types:zone(), gen_id()) -> generation() | undefined.
+meta_get_gen(Zone, GenId) ->
+    case meta_lookup(Zone, GenId, []) of
+        [Gen | _Older] -> Gen;
+        [] -> undefined
+    end.
 
 -spec meta_get_current(emqx_types:zone()) -> gen_id() | undefined.
 meta_get_current(Zone) ->
     meta_lookup(Zone, current, undefined).
 
 -spec meta_lookup(emqx_types:zone(), _K) -> _V.
-meta_lookup(Zone, GenId) ->
-    persistent_term:get(?PERSISTENT_TERM(Zone, GenId)).
+meta_lookup(Zone, K) ->
+    persistent_term:get(?PERSISTENT_TERM(Zone, K)).
 
 -spec meta_lookup(emqx_types:zone(), _K, Default) -> _V | Default.
-meta_lookup(Zone, GenId, Default) ->
-    persistent_term:get(?PERSISTENT_TERM(Zone, GenId), Default).
+meta_lookup(Zone, K, Default) ->
+    persistent_term:get(?PERSISTENT_TERM(Zone, K), Default).
 
 -spec meta_put(emqx_types:zone(), _K, _V) -> ok.
-meta_put(Zone, GenId, Gen) ->
-    persistent_term:put(?PERSISTENT_TERM(Zone, GenId), Gen).
+meta_put(Zone, K, V) ->
+    persistent_term:put(?PERSISTENT_TERM(Zone, K), V).
 
 -spec meta_erase(emqx_types:zone()) -> ok.
 meta_erase(Zone) ->
diff --git a/apps/emqx_replay/test/emqx_replay_local_store_SUITE.erl b/apps/emqx_replay/test/emqx_replay_local_store_SUITE.erl
index d3518d780..edda0f7f6 100644
--- a/apps/emqx_replay/test/emqx_replay_local_store_SUITE.erl
+++ b/apps/emqx_replay/test/emqx_replay_local_store_SUITE.erl
@@ -23,6 +23,25 @@
 
 -define(ZONE, zone(?FUNCTION_NAME)).
 
+-define(DEFAULT_CONFIG,
+    {emqx_replay_message_storage, #{
+        timestamp_bits => 64,
+        topic_bits_per_level => [8, 8, 32, 16],
+        epoch => 5,
+        iteration => #{
+            iterator_refresh => {every, 5}
+        }
+    }}
+).
+
+-define(COMPACT_CONFIG,
+    {emqx_replay_message_storage, #{
+        timestamp_bits => 16,
+        topic_bits_per_level => [16, 16],
+        epoch => 10
+    }}
+).
+
 %% Smoke test for opening and reopening the database
 t_open(_Config) ->
     ok = emqx_replay_local_store_sup:stop_zone(?ZONE),
@@ -128,6 +147,49 @@ t_iterate_long_tail_wildcard(_Config) ->
         lists:sort([binary_to_term(Payload) || Payload <- iterate(?ZONE, TopicFilter, 50)])
     ).
 
+t_create_gen(_Config) ->
+    {ok, 1} = emqx_replay_local_store:create_generation(?ZONE, 5, ?DEFAULT_CONFIG),
+    ?assertEqual(
+        {error, nonmonotonic},
+        emqx_replay_local_store:create_generation(?ZONE, 1, ?DEFAULT_CONFIG)
+    ),
+    ?assertEqual(
+        {error, nonmonotonic},
+        emqx_replay_local_store:create_generation(?ZONE, 5, ?DEFAULT_CONFIG)
+    ),
+    {ok, 2} = emqx_replay_local_store:create_generation(?ZONE, 10, ?COMPACT_CONFIG),
+    Topics = ["foo/bar", "foo/bar/baz"],
+    Timestamps = lists:seq(1, 100),
+    [
+        ?assertEqual(ok, store(?ZONE, PublishedAt, Topic, <<>>))
+     || Topic <- Topics, PublishedAt <- Timestamps
+    ].
+
+t_iterate_multigen(_Config) ->
+    {ok, 1} = emqx_replay_local_store:create_generation(?ZONE, 10, ?COMPACT_CONFIG),
+    {ok, 2} = emqx_replay_local_store:create_generation(?ZONE, 50, ?DEFAULT_CONFIG),
+    {ok, 3} = emqx_replay_local_store:create_generation(?ZONE, 1000, ?DEFAULT_CONFIG),
+    Topics = ["foo/bar", "foo/bar/baz", "a", "a/bar"],
+    Timestamps = lists:seq(1, 100),
+    _ = [
+        store(?ZONE, PublishedAt, Topic, term_to_binary({Topic, PublishedAt}))
+     || Topic <- Topics, PublishedAt <- Timestamps
+    ],
+    ?assertEqual(
+        lists:sort([
+            {Topic, PublishedAt}
+         || Topic <- ["foo/bar", "foo/bar/baz"], PublishedAt <- Timestamps
+        ]),
+        lists:sort([binary_to_term(Payload) || Payload <- iterate(?ZONE, "foo/#", 0)])
+    ),
+    ?assertEqual(
+        lists:sort([
+            {Topic, PublishedAt}
+         || Topic <- ["a", "a/bar"], PublishedAt <- lists:seq(60, 100)
+        ]),
+        lists:sort([binary_to_term(Payload) || Payload <- iterate(?ZONE, "a/#", 60)])
+    ).
+
 store(Zone, PublishedAt, Topic, Payload) ->
     ID = emqx_guid:gen(),
     emqx_replay_local_store:store(Zone, ID, PublishedAt, parse_topic(Topic), Payload).
@@ -161,14 +223,7 @@ end_per_suite(_Config) ->
     ok = application:stop(emqx_replay).
 
 init_per_testcase(TC, Config) ->
-    ok = set_zone_config(zone(TC), #{
-        timestamp_bits => 64,
-        topic_bits_per_level => [8, 8, 32, 16],
-        epoch => 5,
-        iteration => #{
-            iterator_refresh => {every, 5}
-        }
-    }),
+    ok = set_zone_config(zone(TC), ?DEFAULT_CONFIG),
     {ok, _} = emqx_replay_local_store_sup:start_zone(zone(TC)),
     Config.
 
@@ -178,7 +233,5 @@ end_per_testcase(TC, _Config) ->
 zone(TC) ->
     list_to_atom(lists:concat([?MODULE, "_", TC])).
 
-set_zone_config(Zone, Options) ->
-    ok = application:set_env(emqx_replay, zone_config, #{
-        Zone => {emqx_replay_message_storage, Options}
-    }).
+set_zone_config(Zone, Config) ->
+    ok = application:set_env(emqx_replay, zone_config, #{Zone => Config}).