diff --git a/apps/emqx_connector/src/emqx_connector_mysql.erl b/apps/emqx_connector/src/emqx_connector_mysql.erl
index 7df2a7901..6fbbe11c6 100644
--- a/apps/emqx_connector/src/emqx_connector_mysql.erl
+++ b/apps/emqx_connector/src/emqx_connector_mysql.erl
@@ -52,7 +52,6 @@ on_jsonify(#{<<"server">> := Server, <<"user">> := User, <<"database">> := DB,
     }.
 
 %% ===================================================================
-
 on_start(InstId, #{<<"server">> := {Host, Port},
                    <<"database">> := DB,
                    <<"user">> := User,
diff --git a/apps/emqx_data_bridge/src/emqx_data_bridge_api.erl b/apps/emqx_data_bridge/src/emqx_data_bridge_api.erl
index 4de432ca8..1a27351eb 100644
--- a/apps/emqx_data_bridge/src/emqx_data_bridge_api.erl
+++ b/apps/emqx_data_bridge/src/emqx_data_bridge_api.erl
@@ -37,7 +37,7 @@
            }).
 
 -rest_api(#{ name => update_data_bridge
-           , method => 'POST'
+           , method => 'PUT'
            , path => "/data_bridges/:bin:name"
            , func => update_bridge
            , descr => "Update an existing data bridge"
diff --git a/apps/emqx_data_bridge/src/emqx_data_bridge_config_handler.erl b/apps/emqx_data_bridge/src/emqx_data_bridge_config_handler.erl
index 387f2b153..ed21b4ce3 100644
--- a/apps/emqx_data_bridge/src/emqx_data_bridge_config_handler.erl
+++ b/apps/emqx_data_bridge/src/emqx_data_bridge_config_handler.erl
@@ -35,6 +35,7 @@
 start_link() ->
     gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
 
+%% TODO: trigger the `updated` message from emqx_resource.
 notify_updated() ->
     gen_server:cast(?MODULE, updated).
 
@@ -45,6 +46,7 @@ handle_call(_Request, _From, State) ->
     Reply = ok,
     {reply, Reply, State}.
 
+%% TODO: change the config handler as a behavoir that calls back the Mod:format_config/1
 handle_cast(updated, State) ->
     Configs = [format_conf(Data) || Data <- emqx_data_bridge:list_bridges()],
     emqx_config_handler ! {emqx_data_bridge, Configs},
diff --git a/apps/emqx_data_bridge/src/emqx_data_bridge_monitor.erl b/apps/emqx_data_bridge/src/emqx_data_bridge_monitor.erl
index f3b6e6736..521d9721c 100644
--- a/apps/emqx_data_bridge/src/emqx_data_bridge_monitor.erl
+++ b/apps/emqx_data_bridge/src/emqx_data_bridge_monitor.erl
@@ -67,6 +67,8 @@ code_change(_OldVsn, State, _Extra) ->
 load_bridges(Configs) ->
     lists:foreach(fun load_bridge/1, Configs).
 
+%% TODO: move this monitor into emqx_resource
+%% emqx_resource:check_and_create_local(ResourceId, ResourceType, Config, #{keep_retry => true}).
 load_bridge(#{<<"name">> := Name, <<"type">> := Type,
               <<"config">> := Config}) ->
     case emqx_resource:check_and_create_local(
diff --git a/apps/emqx_resource/src/emqx_resource.erl b/apps/emqx_resource/src/emqx_resource.erl
index 53533c758..5a9b21408 100644
--- a/apps/emqx_resource/src/emqx_resource.erl
+++ b/apps/emqx_resource/src/emqx_resource.erl
@@ -255,13 +255,9 @@ call_stop(InstId, Mod, ResourceState) ->
 -spec call_config_merge(module(), resource_config(), resource_config(), term()) ->
     resource_config().
 call_config_merge(Mod, OldConfig, NewConfig, Params) ->
-    case erlang:function_exported(Mod, on_jsonify, 1) of
-        true ->
-            ?SAFE_CALL(Mod:on_config_merge(OldConfig, NewConfig, Params));
-        false when is_map(OldConfig), is_map(NewConfig) ->
-            maps:merge(OldConfig, NewConfig);
-        false ->
-            NewConfig
+    case erlang:function_exported(Mod, on_config_merge, 3) of
+        true -> ?SAFE_CALL(Mod:on_config_merge(OldConfig, NewConfig, Params));
+        false -> NewConfig
     end.
 
 -spec call_jsonify(module(), resource_config()) -> jsx:json_term().