diff --git a/apps/emqx_ds_shared_sub/src/emqx_ds_shared_sub_leader.erl b/apps/emqx_ds_shared_sub/src/emqx_ds_shared_sub_leader.erl
index f0d194dfc..510d6a45f 100644
--- a/apps/emqx_ds_shared_sub/src/emqx_ds_shared_sub_leader.erl
+++ b/apps/emqx_ds_shared_sub/src/emqx_ds_shared_sub_leader.erl
@@ -71,7 +71,7 @@
     rank_progress := emqx_ds_shared_sub_leader_rank_progress:t(),
 
     %%
-    %% Ephimeral data, should not be persisted
+    %% Ephemeral data, should not be persisted
     %%
     agents := #{
         emqx_ds_shared_sub_proto:agent() => agent_state()
diff --git a/apps/emqx_ds_shared_sub/src/emqx_ds_shared_sub_leader_rank_progress.erl b/apps/emqx_ds_shared_sub/src/emqx_ds_shared_sub_leader_rank_progress.erl
index 5cde51f16..fa611463d 100644
--- a/apps/emqx_ds_shared_sub/src/emqx_ds_shared_sub_leader_rank_progress.erl
+++ b/apps/emqx_ds_shared_sub/src/emqx_ds_shared_sub_leader_rank_progress.erl
@@ -9,7 +9,8 @@
 -export([
     init/0,
     set_replayed/2,
-    add_streams/2
+    add_streams/2,
+    replayed_up_to/2
 ]).
 
 %% "shard"
@@ -87,6 +88,15 @@ add_streams(StreamsWithRanks, State) ->
         SortedStreamsWithRanks
     ).
 
+-spec replayed_up_to(emqx_ds:rank_x(), t()) -> emqx_ds:rank_y().
+replayed_up_to(RankX, State) ->
+    case State of
+        #{RankX := #{min_y := MinY}} ->
+            MinY;
+        _ ->
+            undefined
+    end.
+
 %%--------------------------------------------------------------------
 %% Internal functions
 %%--------------------------------------------------------------------
@@ -110,7 +120,7 @@ add_stream({{RankX, RankY}, Stream}, State0) ->
 update_min_y([{RankY, RankYStreams} | Rest] = Ys) ->
     case {has_unreplayed_streams(RankYStreams), Rest} of
         {true, _} ->
-            {RankY, maps:from_list(Ys)};
+            {RankY - 1, maps:from_list(Ys)};
         {false, []} ->
             {RankY - 1, #{}};
         {false, _} ->
@@ -122,3 +132,40 @@ has_unreplayed_streams(RankYStreams) ->
         fun(IsReplayed) -> not IsReplayed end,
         maps:values(RankYStreams)
     ).
+
+-ifdef(TEST).
+-include_lib("eunit/include/eunit.hrl").
+
+add_streams_set_replayed_test() ->
+    State0 = init(),
+    {_, State1} = add_streams(
+        [
+            {{shard1, 1}, s111},
+            {{shard1, 1}, s112},
+            {{shard1, 2}, s121},
+            {{shard1, 2}, s122},
+            {{shard1, 3}, s131},
+            {{shard1, 4}, s141},
+
+            {{shard3, 5}, s51}
+        ],
+        State0
+    ),
+    ?assertEqual(0, replayed_up_to(shard1, State1)),
+
+    State2 = set_replayed({{shard1, 1}, s111}, State1),
+    State3 = set_replayed({{shard1, 3}, s131}, State2),
+    ?assertEqual(0, replayed_up_to(shard1, State3)),
+    State4 = set_replayed({{shard1, 1}, s112}, State3),
+    ?assertEqual(1, replayed_up_to(shard1, State4)),
+
+    State5 = set_replayed({{shard1, 2}, s121}, State4),
+    State6 = set_replayed({{shard1, 2}, s122}, State5),
+
+    ?assertEqual(3, replayed_up_to(shard1, State6)),
+
+    State7 = set_replayed({{shard1, 4}, s141}, State6),
+    ?assertEqual(3, replayed_up_to(shard1, State7)).
+
+%% -ifdef(TEST) end
+-endif.