diff --git a/proto/greptime/v1/meta/common.proto b/proto/greptime/v1/meta/common.proto
index 13f7322..0c98406 100644
--- a/proto/greptime/v1/meta/common.proto
+++ b/proto/greptime/v1/meta/common.proto
@@ -10,6 +10,12 @@ message RequestHeader {
   uint64 cluster_id = 2;
   // member_id is the ID of the sender server.
   uint64 member_id = 3;
+  Role role = 4;
+}
+
+enum Role {
+  DATANODE = 0;
+  FRONTEND = 1;
 }
 
 message ResponseHeader {
@@ -37,9 +43,9 @@ message TableName {
 
 message TimeInterval {
   // The unix timestamp in millis of the start of this period.
-  uint64 start_timestamp_millis = 1;
+  int64 start_timestamp_millis = 1;
   // The unix timestamp in millis of the end of this period.
-  uint64 end_timestamp_millis = 2;
+  int64 end_timestamp_millis = 2;
 }
 
 message KeyValue {
diff --git a/proto/greptime/v1/meta/heartbeat.proto b/proto/greptime/v1/meta/heartbeat.proto
index 41b28cd..c05220b 100644
--- a/proto/greptime/v1/meta/heartbeat.proto
+++ b/proto/greptime/v1/meta/heartbeat.proto
@@ -32,6 +32,7 @@ message HeartbeatRequest {
   repeated RegionStat region_stats = 6;
   // Follower nodes and stats, empty on follower nodes
   repeated ReplicaStat replica_stats = 7;
+  repeated MailboxMessage mailbox_messages = 8;
 }
 
 message NodeStat {
@@ -80,7 +81,7 @@ message ReplicaStat {
 message HeartbeatResponse {
   ResponseHeader header = 1;
 
-  repeated bytes payload = 2;
+  repeated MailboxMessage mailbox_messages = 2;
 }
 
 message AskLeaderRequest {
@@ -92,3 +93,19 @@ message AskLeaderResponse {
 
   Peer leader = 2;
 }
+
+message MailboxMessage {
+  // The id is used to associate request and response.
+  uint64 id = 1;
+  // The following information plays a bigger role in making messages traceable and facilitating debugging.
+  string subject = 2;
+  string from = 3;
+  string to = 4;
+  // The unix timestamp in milliseconds.
+  int64 timestamp_millis = 5;
+
+  // The message body.
+  oneof payload {
+    string json = 6;
+  }
+}
diff --git a/src/v1/meta.rs b/src/v1/meta.rs
index 668c9bd..ba55931 100644
--- a/src/v1/meta.rs
+++ b/src/v1/meta.rs
@@ -62,6 +62,7 @@ impl RequestHeader {
             protocol_version: PROTOCOL_VERSION,
             cluster_id,
             member_id,
+            role: 0,
         }
     }
 }