diff --git a/apps/emqx_connector/src/emqx_connector_mqtt.erl b/apps/emqx_connector/src/emqx_connector_mqtt.erl
index bb8cc00d1..1efe6f3e0 100644
--- a/apps/emqx_connector/src/emqx_connector_mqtt.erl
+++ b/apps/emqx_connector/src/emqx_connector_mqtt.erl
@@ -15,10 +15,6 @@
 %%--------------------------------------------------------------------
 -module(emqx_connector_mqtt).
 
--include("emqx_connector.hrl").
-
--include_lib("typerefl/include/types.hrl").
--include_lib("hocon/include/hoconsc.hrl").
 -include_lib("emqx/include/logger.hrl").
 
 -behaviour(supervisor).
@@ -47,52 +43,6 @@
 
 -export([on_async_result/2]).
 
--behaviour(hocon_schema).
-
--import(hoconsc, [mk/2]).
-
--export([
-    roots/0,
-    fields/1
-]).
-
-%%=====================================================================
-%% Hocon schema
-roots() ->
-    fields("config").
-
-fields("config") ->
-    emqx_connector_mqtt_schema:fields("config");
-fields("get") ->
-    [
-        {num_of_bridges,
-            mk(
-                integer(),
-                #{desc => ?DESC("num_of_bridges")}
-            )}
-    ] ++ fields("post");
-fields("put") ->
-    emqx_connector_mqtt_schema:fields("server_configs");
-fields("post") ->
-    [
-        {type,
-            mk(
-                mqtt,
-                #{
-                    required => true,
-                    desc => ?DESC("type")
-                }
-            )},
-        {name,
-            mk(
-                binary(),
-                #{
-                    required => true,
-                    desc => ?DESC("name")
-                }
-            )}
-    ] ++ fields("put").
-
 %% ===================================================================
 %% supervisor APIs
 start_link() ->
@@ -313,7 +263,7 @@ maybe_put_fields(Fields, Conf, Acc0) ->
 ms_to_s(Ms) ->
     erlang:ceil(Ms / 1000).
 
-clientid(Id, _Conf = #{clientid_prefix := Prefix = <<_/binary>>}) ->
+clientid(Id, _Conf = #{clientid_prefix := Prefix}) when is_binary(Prefix) ->
     iolist_to_binary([Prefix, ":", Id, ":", atom_to_list(node())]);
 clientid(Id, _Conf) ->
     iolist_to_binary([Id, ":", atom_to_list(node())]).
diff --git a/apps/emqx_connector/src/mqtt/emqx_connector_mqtt_msg.erl b/apps/emqx_connector/src/mqtt/emqx_connector_mqtt_msg.erl
index df1114483..8fc70405f 100644
--- a/apps/emqx_connector/src/mqtt/emqx_connector_mqtt_msg.erl
+++ b/apps/emqx_connector/src/mqtt/emqx_connector_mqtt_msg.erl
@@ -17,12 +17,9 @@
 -module(emqx_connector_mqtt_msg).
 
 -export([
-    to_binary/1,
-    from_binary/1,
     make_pub_vars/2,
     to_remote_msg/2,
-    to_broker_msg/3,
-    estimate_size/1
+    to_broker_msg/3
 ]).
 
 -export([
@@ -143,25 +140,6 @@ replace_simple_var(Tokens, Data) when is_list(Tokens) ->
 replace_simple_var(Val, _Data) ->
     Val.
 
-%% @doc Make `binary()' in order to make iodata to be persisted on disk.
--spec to_binary(msg()) -> binary().
-to_binary(Msg) -> term_to_binary(Msg).
-
-%% @doc Unmarshal binary into `msg()'.
--spec from_binary(binary()) -> msg().
-from_binary(Bin) -> binary_to_term(Bin).
-
-%% @doc Estimate the size of a message.
-%% Count only the topic length + payload size
-%% There is no topic and payload for event message. So count all `Msg` term
--spec estimate_size(msg()) -> integer().
-estimate_size(#message{topic = Topic, payload = Payload}) ->
-    size(Topic) + size(Payload);
-estimate_size(#{topic := Topic, payload := Payload}) ->
-    size(Topic) + size(Payload);
-estimate_size(Term) ->
-    erlang:external_size(Term).
-
 set_headers(Val, Msg) ->
     emqx_message:set_headers(Val, Msg).
 topic(undefined, Topic) -> Topic;