diff --git a/mini-program/database/sql/001_init_chat.sql b/mini-program/database/sql/001_init_chat.sql
index 6ebf6a7..a8c6a02 100644
--- a/mini-program/database/sql/001_init_chat.sql
+++ b/mini-program/database/sql/001_init_chat.sql
@@ -51,9 +51,8 @@ CREATE TABLE IF NOT EXISTS chat_user_auth (
 
 CREATE TABLE IF NOT EXISTS chat_conversation (
   id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
-  title VARCHAR(128) NULL,
-  conversation_type TINYINT UNSIGNED NOT NULL DEFAULT 1 COMMENT '1-direct 2-group',
-  member_signature CHAR(64) NOT NULL COMMENT 'sha256 of sorted member user_ids, e.g. sha256("1,2")',
+  user_low_id BIGINT UNSIGNED NOT NULL COMMENT 'Smaller user_id in direct chat pair',
+  user_high_id BIGINT UNSIGNED NOT NULL COMMENT 'Larger user_id in direct chat pair',
   status TINYINT UNSIGNED NOT NULL DEFAULT 1 COMMENT '1-active 2-archived',
   last_seq BIGINT UNSIGNED NOT NULL DEFAULT 0,
   message_count BIGINT UNSIGNED NOT NULL DEFAULT 0,
@@ -62,23 +61,15 @@ CREATE TABLE IF NOT EXISTS chat_conversation (
   created_at DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
   updated_at DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
   PRIMARY KEY (id),
-  UNIQUE KEY uk_type_member_signature (conversation_type, member_signature),
-  KEY idx_last_message_at (last_message_at)
-) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
-
-CREATE TABLE IF NOT EXISTS chat_conversation_member (
-  conversation_id BIGINT UNSIGNED NOT NULL,
-  user_id BIGINT UNSIGNED NOT NULL,
-  member_role TINYINT UNSIGNED NOT NULL DEFAULT 2 COMMENT '1-owner 2-member',
-  joined_at DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3),
-  left_at DATETIME(3) NULL,
-  PRIMARY KEY (conversation_id, user_id),
-  KEY idx_user_conversation (user_id, conversation_id),
-  CONSTRAINT fk_member_conv
-    FOREIGN KEY (conversation_id) REFERENCES chat_conversation(id)
+  UNIQUE KEY uk_direct_pair (user_low_id, user_high_id),
+  KEY idx_last_message_at (last_message_at),
+  KEY idx_user_low_id (user_low_id),
+  KEY idx_user_high_id (user_high_id),
+  CONSTRAINT fk_conv_user_low
+    FOREIGN KEY (user_low_id) REFERENCES chat_user(id)
     ON DELETE CASCADE,
-  CONSTRAINT fk_member_user
-    FOREIGN KEY (user_id) REFERENCES chat_user(id)
+  CONSTRAINT fk_conv_user_high
+    FOREIGN KEY (user_high_id) REFERENCES chat_user(id)
     ON DELETE CASCADE
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
 
@@ -203,9 +194,8 @@ VALUES
 
 INSERT INTO chat_conversation (
   id,
-  title,
-  conversation_type,
-  member_signature,
+  user_low_id,
+  user_high_id,
   status,
   last_seq,
   message_count,
@@ -217,45 +207,17 @@ INSERT INTO chat_conversation (
 VALUES
   (
     1,
-    'Direct Chat',
     1,
-    '17f8af97ad4a7f7639a4c9171d5185cbafb85462877a4746c21bdb0a4f940ca0',
+    2,
     1,
-    4,
-    4,
-    'user: Great, explain how to solve it.',
-    '2026-03-25 10:00:30.000',
+    5,
+    5,
+    'user: Thanks, I understand now.',
+    '2026-03-25 10:00:40.000',
     '2026-03-25 10:00:00.000',
-    '2026-03-25 10:00:30.000'
-  ),
-  (
-    2,
-    'Family Group',
-    2,
-    '8a6ae15122001229edb8866f56e342af12ae8187203c3e3b33931743e7c0c48d',
-    1,
-    3,
-    3,
-    'user: Okay, we will wait in the living room.',
-    '2026-03-25 21:16:10.000',
-    '2026-03-25 21:15:00.000',
-    '2026-03-25 21:16:10.000'
+    '2026-03-25 10:00:40.000'
   );
 
-INSERT INTO chat_conversation_member (
-  conversation_id,
-  user_id,
-  member_role,
-  joined_at,
-  left_at
-)
-VALUES
-  (1, 1, 1, '2026-03-25 10:00:00.000', NULL),
-  (1, 2, 2, '2026-03-25 10:00:00.000', NULL),
-  (2, 1, 1, '2026-03-25 21:15:00.000', NULL),
-  (2, 2, 2, '2026-03-25 21:15:00.000', NULL),
-  (2, 3, 2, '2026-03-25 21:15:00.000', NULL);
-
 INSERT INTO chat_message (
   id,
   conversation_id,
@@ -328,44 +290,16 @@ VALUES
     '2026-03-25 10:00:30.000'
   ),
   (
-    2001,
+    1005,
+    1,
+    5,
     2,
     1,
     1,
-    1,
-    1,
-    'Dinner at 7?',
+    'Thanks, I understand now.',
     JSON_OBJECT('lang', 'en'),
     NULL,
     NULL,
-    'c2-m1',
-    '2026-03-25 21:15:08.000'
-  ),
-  (
-    2002,
-    2,
-    2,
-    3,
-    1,
-    2,
-    NULL,
-    JSON_OBJECT('note', 'voice message'),
-    'audios/family-group-001.mp3',
-    95000,
-    'c2-m2',
-    '2026-03-25 21:15:30.000'
-  ),
-  (
-    2003,
-    2,
-    3,
-    2,
-    1,
-    1,
-    'Okay, we will wait in the living room.',
-    JSON_OBJECT('lang', 'en'),
-    NULL,
-    NULL,
-    'c2-m3',
-    '2026-03-25 21:16:10.000'
+    'c1-m5',
+    '2026-03-25 10:00:40.000'
   );