diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c128a6e8..7830de07 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -31,6 +31,36 @@ jobs:
         working-directory: backend
         run: go vet ./...
 
+  backend-postgres:
+    name: Backend (PostgreSQL concurrency)
+    runs-on: ubuntu-latest
+    services:
+      postgres:
+        image: postgres:16-alpine
+        env:
+          POSTGRES_DB: gochat_test
+          POSTGRES_USER: postgres
+          POSTGRES_PASSWORD: postgres
+        ports:
+          - 5432:5432
+        options: >-
+          --health-cmd "pg_isready -U postgres -d gochat_test"
+          --health-interval 5s
+          --health-timeout 5s
+          --health-retries 5
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: backend/go.mod
+          cache-dependency-path: backend/go.sum
+      - name: Test auto-assignment concurrency
+        working-directory: backend
+        env:
+          GOCHAT_TEST_DB: postgres
+          GOCHAT_TEST_DB_URL: postgres://postgres:postgres@localhost:5432/gochat_test?sslmode=disable
+        run: go test ./internal/autoassignment -run '^TestAssignmentServiceOnlyOneConcurrentWorkerWinsPostgres$' -count=3
+
   frontend:
     name: Frontend Build
     runs-on: ubuntu-latest
diff --git a/backend/internal/autoassignment/coverage9_test.go b/backend/internal/autoassignment/coverage9_test.go
index 957626b1..6a8052cf 100644
--- a/backend/internal/autoassignment/coverage9_test.go
+++ b/backend/internal/autoassignment/coverage9_test.go
@@ -3,6 +3,8 @@ package autoassignment
 import (
 	"context"
 	"fmt"
+	"net/url"
+	"os"
 	"strings"
 	"sync"
 	"sync/atomic"
@@ -14,11 +16,23 @@ import (
 	"github.com/gochat/gochat/internal/model"
 	"github.com/redis/go-redis/v9"
 	"github.com/stretchr/testify/require"
+	"gorm.io/driver/postgres"
 	"gorm.io/driver/sqlite"
 	"gorm.io/gorm"
 	"gorm.io/gorm/logger"
 )
 
+func migrateFullAADB_Cov9(t *testing.T, db *gorm.DB) {
+	t.Helper()
+	require.NoError(t, db.AutoMigrate(
+		&model.Account{}, &model.User{}, &model.AccountUser{},
+		&model.Inbox{}, &model.InboxMember{}, &model.Contact{}, &model.ContactInbox{},
+		&model.Conversation{}, &model.Message{},
+		&AssignmentPolicy{}, &InboxAssignmentPolicy{},
+		&model.AgentCapacityPolicy{}, &model.InboxCapacityLimit{},
+	))
+}
+
 func setupFullAADB_Cov9(t *testing.T) (*gorm.DB, *redis.Client) {
 	t.Helper()
 	db, err := gorm.Open(sqlite.Open(fmt.Sprintf("file:%s?mode=memory&cache=shared&_busy_timeout=5000", strings.ReplaceAll(t.Name(), "/", "_"))), &gorm.Config{Logger: logger.Default.LogMode(logger.Silent)})
@@ -26,13 +40,49 @@ func setupFullAADB_Cov9(t *testing.T) (*gorm.DB, *redis.Client) {
 	sqlDB, err := db.DB()
 	require.NoError(t, err)
 	t.Cleanup(func() { _ = sqlDB.Close() })
-	require.NoError(t, db.AutoMigrate(
-		&model.Account{}, &model.User{}, &model.AccountUser{},
-		&model.Inbox{}, &model.InboxMember{}, &model.Contact{}, &model.ContactInbox{},
-		&model.Conversation{}, &model.Message{},
-		&AssignmentPolicy{}, &InboxAssignmentPolicy{},
-		&model.AgentCapacityPolicy{}, &model.InboxCapacityLimit{},
-	))
+	migrateFullAADB_Cov9(t, db)
+	mr := miniredis.RunT(t)
+	rdb := redis.NewClient(&redis.Options{Addr: mr.Addr()})
+	t.Cleanup(func() { _ = rdb.Close() })
+	return db, rdb
+}
+
+func setupFullAAPostgresDB_Cov9(t *testing.T) (*gorm.DB, *redis.Client) {
+	t.Helper()
+	dsn := os.Getenv("GOCHAT_TEST_DB_URL")
+	if dsn == "" {
+		dsn = "postgres://postgres:postgres@localhost:5432/gochat_test?sslmode=disable"
+	}
+	admin, err := gorm.Open(postgres.Open(dsn), &gorm.Config{Logger: logger.Default.LogMode(logger.Silent)})
+	require.NoError(t, err)
+	adminDB, err := admin.DB()
+	require.NoError(t, err)
+	schema := fmt.Sprintf("autoassignment_%d", time.Now().UnixNano())
+	require.NoError(t, admin.Exec("CREATE SCHEMA "+schema).Error)
+	t.Cleanup(func() {
+		_ = admin.Exec("DROP SCHEMA " + schema + " CASCADE").Error
+		_ = adminDB.Close()
+	})
+
+	if strings.HasPrefix(dsn, "postgres://") || strings.HasPrefix(dsn, "postgresql://") {
+		dsnURL, parseErr := url.Parse(dsn)
+		require.NoError(t, parseErr)
+		query := dsnURL.Query()
+		query.Set("search_path", schema)
+		dsnURL.RawQuery = query.Encode()
+		dsn = dsnURL.String()
+	} else {
+		dsn += " search_path=" + schema
+	}
+	db, err := gorm.Open(postgres.Open(dsn), &gorm.Config{
+		Logger:                                   logger.Default.LogMode(logger.Silent),
+		DisableForeignKeyConstraintWhenMigrating: true,
+	})
+	require.NoError(t, err)
+	sqlDB, err := db.DB()
+	require.NoError(t, err)
+	t.Cleanup(func() { _ = sqlDB.Close() })
+	migrateFullAADB_Cov9(t, db)
 	mr := miniredis.RunT(t)
 	rdb := redis.NewClient(&redis.Options{Addr: mr.Addr()})
 	t.Cleanup(func() { _ = rdb.Close() })
@@ -168,6 +218,19 @@ func TestAssignmentServiceAutoAssignmentDoesNotOverwriteNewConversationState(t *
 
 func TestAssignmentServiceOnlyOneConcurrentWorkerWins(t *testing.T) {
 	db, rdb := setupFullAADB_Cov9(t)
+	testAssignmentServiceOnlyOneConcurrentWorkerWins(t, db, rdb)
+}
+
+func TestAssignmentServiceOnlyOneConcurrentWorkerWinsPostgres(t *testing.T) {
+	if os.Getenv("GOCHAT_TEST_DB") != "postgres" {
+		t.Skip("PostgreSQL concurrency test")
+	}
+	db, rdb := setupFullAAPostgresDB_Cov9(t)
+	testAssignmentServiceOnlyOneConcurrentWorkerWins(t, db, rdb)
+}
+
+func testAssignmentServiceOnlyOneConcurrentWorkerWins(t *testing.T, db *gorm.DB, rdb *redis.Client) {
+	t.Helper()
 	account, agent, inbox, conversation := seedAssignableConversation_Cov9(t, db)
 	db = db.Session(&gorm.Session{SkipDefaultTransaction: true})
 	sqlDB, err := db.DB()