diff --git a/apps/emqx_bridge_s3/src/emqx_bridge_s3_connector.erl b/apps/emqx_bridge_s3/src/emqx_bridge_s3_connector.erl
index a3edc717e..f9d3af478 100644
--- a/apps/emqx_bridge_s3/src/emqx_bridge_s3_connector.erl
+++ b/apps/emqx_bridge_s3/src/emqx_bridge_s3_connector.erl
@@ -394,8 +394,8 @@ iolist_to_string(IOList) ->
 
 %% `emqx_connector_aggreg_delivery` APIs
 
--spec init_transfer_state(buffer(), map()) -> emqx_s3_upload:t().
-init_transfer_state(Buffer, Opts) ->
+-spec init_transfer_state(buffer_map(), map()) -> emqx_s3_upload:t().
+init_transfer_state(BufferMap, Opts) ->
     #{
         bucket := Bucket,
         upload_options := UploadOpts,
@@ -403,11 +403,11 @@ init_transfer_state(Buffer, Opts) ->
         uploader_config := UploaderConfig
     } = Opts,
     Client = emqx_s3_client:create(Bucket, Config),
-    Key = mk_object_key(Buffer, Opts),
+    Key = mk_object_key(BufferMap, Opts),
     emqx_s3_upload:new(Client, Key, UploadOpts, UploaderConfig).
 
-mk_object_key(Buffer, #{action := Name, key := Template}) ->
-    emqx_template:render_strict(Template, {?MODULE, {Name, Buffer}}).
+mk_object_key(BufferMap, #{action := Name, key := Template}) ->
+    emqx_template:render_strict(Template, {?MODULE, {Name, BufferMap}}).
 
 process_append(Writes, Upload0) ->
     {ok, Upload} = emqx_s3_upload:append(Writes, Upload0),
@@ -441,22 +441,22 @@ process_terminate(Upload) ->
 
 %% `emqx_template` APIs
 
--spec lookup(emqx_template:accessor(), {_Name, buffer()}) ->
+-spec lookup(emqx_template:accessor(), {_Name, buffer_map()}) ->
     {ok, integer() | string()} | {error, undefined}.
 lookup([<<"action">>], {Name, _Buffer}) ->
     {ok, mk_fs_safe_string(Name)};
-lookup(Accessor, {_Name, Buffer = #buffer{}}) ->
+lookup(Accessor, {_Name, Buffer = #{}}) ->
     lookup_buffer_var(Accessor, Buffer);
 lookup(_Accessor, _Context) ->
     {error, undefined}.
 
-lookup_buffer_var([<<"datetime">>, Format], #buffer{since = Since}) ->
+lookup_buffer_var([<<"datetime">>, Format], #{since := Since}) ->
     {ok, format_timestamp(Since, Format)};
-lookup_buffer_var([<<"datetime_until">>, Format], #buffer{until = Until}) ->
+lookup_buffer_var([<<"datetime_until">>, Format], #{until := Until}) ->
     {ok, format_timestamp(Until, Format)};
-lookup_buffer_var([<<"sequence">>], #buffer{seq = Seq}) ->
+lookup_buffer_var([<<"sequence">>], #{seq := Seq}) ->
     {ok, Seq};
-lookup_buffer_var([<<"node">>], #buffer{}) ->
+lookup_buffer_var([<<"node">>], #{}) ->
     {ok, mk_fs_safe_string(atom_to_binary(erlang:node()))};
 lookup_buffer_var(_Binding, _Context) ->
     {error, undefined}.
diff --git a/apps/emqx_connector_aggregator/include/emqx_connector_aggregator.hrl b/apps/emqx_connector_aggregator/include/emqx_connector_aggregator.hrl
index eeef351f2..07d4a414f 100644
--- a/apps/emqx_connector_aggregator/include/emqx_connector_aggregator.hrl
+++ b/apps/emqx_connector_aggregator/include/emqx_connector_aggregator.hrl
@@ -13,3 +13,11 @@
 }).
 
 -type buffer() :: #buffer{}.
+
+-type buffer_map() :: #{
+    since := emqx_connector_aggregator:timestamp(),
+    until := emqx_connector_aggregator:timestamp(),
+    seq := non_neg_integer(),
+    filename := file:filename(),
+    max_records := pos_integer() | undefined
+}.
diff --git a/apps/emqx_connector_aggregator/src/emqx_connector_aggreg_delivery.erl b/apps/emqx_connector_aggregator/src/emqx_connector_aggreg_delivery.erl
index 5f946dd7c..70f54a385 100644
--- a/apps/emqx_connector_aggregator/src/emqx_connector_aggreg_delivery.erl
+++ b/apps/emqx_connector_aggregator/src/emqx_connector_aggreg_delivery.erl
@@ -42,7 +42,7 @@
 
 -type transfer_state() :: term().
 
--callback init_transfer_state(buffer(), map()) -> transfer_state().
+-callback init_transfer_state(buffer_map(), map()) -> transfer_state().
 
 -callback process_append(iodata(), transfer_state()) -> transfer_state().
 
@@ -75,12 +75,13 @@ init_delivery(
         callback_module := Mod
     }
 ) ->
+    BufferMap = emqx_connector_aggregator:buffer_to_map(Buffer),
     #delivery{
         name = Name,
         callback_module = Mod,
         container = mk_container(ContainerOpts),
         reader = Reader,
-        transfer = Mod:init_transfer_state(Buffer, Opts),
+        transfer = Mod:init_transfer_state(BufferMap, Opts),
         empty = true
     }.
 
diff --git a/apps/emqx_connector_aggregator/src/emqx_connector_aggregator.erl b/apps/emqx_connector_aggregator/src/emqx_connector_aggregator.erl
index 01b330646..f3936fd54 100644
--- a/apps/emqx_connector_aggregator/src/emqx_connector_aggregator.erl
+++ b/apps/emqx_connector_aggregator/src/emqx_connector_aggregator.erl
@@ -16,7 +16,8 @@
     start_link/2,
     push_records/3,
     tick/2,
-    take_error/1
+    take_error/1,
+    buffer_to_map/1
 ]).
 
 -behaviour(gen_server).
@@ -72,6 +73,15 @@ tick(Name, Timestamp) ->
 take_error(Name) ->
     gen_server:call(?SRVREF(Name), take_error).
 
+buffer_to_map(#buffer{} = Buffer) ->
+    #{
+        since => Buffer#buffer.since,
+        until => Buffer#buffer.until,
+        seq => Buffer#buffer.seq,
+        filename => Buffer#buffer.filename,
+        max_records => Buffer#buffer.max_records
+    }.
+
 %%
 
 write_records_limited(Name, Buffer = #buffer{max_records = undefined}, Records) ->