diff --git a/database/migrations/2025_11_29_120000_update_stat_user_unique_constraint.php b/database/migrations/2025_11_29_120000_update_stat_user_unique_constraint.php
new file mode 100644
index 0000000..6ae1b83
--- /dev/null
+++ b/database/migrations/2025_11_29_120000_update_stat_user_unique_constraint.php
@@ -0,0 +1,55 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     * 
+     * Updates the unique constraint on v2_stat_user to include server_id,
+     * allowing per-node user traffic tracking.
+     */
+    public function up(): void
+    {
+        if (config('database.default') === 'sqlite') {
+            // SQLite uses explicit WHERE queries in code, no constraint changes needed
+            return;
+        }
+
+        Schema::table('v2_stat_user', function (Blueprint $table) {
+            // Drop the old unique constraint that doesn't include server_id
+            $table->dropUnique('server_rate_user_id_record_at');
+            
+            // Add new unique constraint including server_id
+            // Note: NULL server_id values (legacy) are treated as distinct in MySQL
+            $table->unique(
+                ['user_id', 'server_id', 'server_rate', 'record_at', 'record_type'],
+                'stat_user_unique_idx'
+            );
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        if (config('database.default') === 'sqlite') {
+            return;
+        }
+
+        Schema::table('v2_stat_user', function (Blueprint $table) {
+            // Drop new constraint
+            $table->dropUnique('stat_user_unique_idx');
+            
+            // Restore original constraint
+            $table->unique(
+                ['server_rate', 'user_id', 'record_at'],
+                'server_rate_user_id_record_at'
+            );
+        });
+    }
+};