diff --git a/etc/emqx.conf b/etc/emqx.conf
index 98e44f4a8..e8f08b827 100644
--- a/etc/emqx.conf
+++ b/etc/emqx.conf
@@ -603,9 +603,9 @@ zone.external.force_gc_policy = 1000|1MB
 ## Numbers delimited by `|'. Zero or negative is to disable.
 ##
 ## Default:
-##   - 8000|800MB on ARCH_64 system
-##   - 1000|100MB on ARCH_32 sytem
-## zone.external.force_shutdown_policy = 8000|800MB
+##   - 10000|32MB on ARCH_64 system
+##   - 10000|16MB on ARCH_32 sytem
+## zone.external.force_shutdown_policy = 10000|32MB
 
 ## Maximum MQTT packet size allowed.
 ##
@@ -798,17 +798,17 @@ zone.internal.max_subscriptions = 0
 ## See zone.$name.max_inflight
 ##
 ## Value: Number
-zone.internal.max_inflight = 32
+zone.internal.max_inflight = 128
 
 ## See zone.$name.max_awaiting_rel
 ##
 ## Value: Number
-zone.internal.max_awaiting_rel = 100
+zone.internal.max_awaiting_rel = 1000
 
 ## See zone.$name.max_mqueue_len
 ##
 ## Value: Number >= 0
-zone.internal.max_mqueue_len = 1000
+zone.internal.max_mqueue_len = 10000
 
 ## Whether to enqueue Qos0 messages.
 ##
@@ -820,6 +820,13 @@ zone.internal.mqueue_store_qos0 = true
 ## Value: on | off
 zone.internal.enable_flapping_detect = off
 
+## See zone.$name.force_shutdown_policy
+##
+## Default:
+##   - 10000|32MB on ARCH_64 system
+##   - 10000|16MB on ARCH_32 sytem
+zone.internal.force_shutdown_policy = 100000|256MB
+
 ## All the topics will be prefixed with the mountpoint path if this option is enabled.
 ##
 ## Variables in mountpoint path:
@@ -829,12 +836,6 @@ zone.internal.enable_flapping_detect = off
 ## Value: String
 ## zone.internal.mountpoint = cloudbound/
 
-## Whether use username replace client id
-##
-## Value: boolean
-## Default: false
-zone.internal.use_username_as_clientid = false
-
 ## Whether to ignore loop delivery of messages.(for mqtt v3.1.1)
 ##
 ## Value: true | false
@@ -1050,14 +1051,14 @@ listener.tcp.internal.send_timeout_close = on
 ## See: listener.tcp.$name.recbuf
 ##
 ## Value: Bytes
-## listener.tcp.internal.recbuf = 16KB
+listener.tcp.internal.recbuf = 64KB
 
 ## The TCP send buffer(os kernel) for internal MQTT connections.
 ##
 ## See: http://erlang.org/doc/man/inet.html
 ##
 ## Value: Bytes
-## listener.tcp.internal.sndbuf = 16KB
+listener.tcp.internal.sndbuf = 64KB
 
 ## The size of the user-level software buffer used by the driver.
 ##
diff --git a/priv/emqx.schema b/priv/emqx.schema
index 54e5f0f4c..bbd0fb4ab 100644
--- a/priv/emqx.schema
+++ b/priv/emqx.schema
@@ -967,9 +967,9 @@ end}.
                     {DefaultLen, DefaultSize} =
                         case WordSize = erlang:system_info(wordsize) of
                             8 -> % arch_64
-                              {8000, cuttlefish_bytesize:parse("800MB")};
+                              {10000, cuttlefish_bytesize:parse("32MB")};
                             4 -> % arch_32
-                              {1000, cuttlefish_bytesize:parse("100MB")}
+                              {10000, cuttlefish_bytesize:parse("16MB")}
                         end,
                     {force_shutdown_policy, #{message_queue_len => DefaultLen,
                                               max_heap_size => DefaultSize div WordSize