perf(go): simplify realtime plate lookup

go/vehicle-gateway/internal/realtime/snapshot_writer.go

@@ -288,7 +288,7 @@ func (r *BindingPlateResolver) PlateByVIN(ctx context.Context, vin string) (stri
 	if vin == "" {
 		return "", sql.ErrNoRows
 	}
-	query := "SELECT plate FROM " + r.table + " WHERE vin = ? AND plate IS NOT NULL AND plate <> '' ORDER BY updated_at DESC LIMIT 1"
+	query := "SELECT plate FROM " + r.table + " WHERE vin = ? AND plate IS NOT NULL AND plate <> ''"
 	var plate string
 	err := r.queryer.QueryRowContext(ctx, query, vin).Scan(&plate)
 	if err != nil {

go/vehicle-gateway/internal/realtime/snapshot_writer_test.go

@@ -216,6 +216,28 @@ func TestSnapshotWriterBackfillsPlateFromBindingByVIN(t *testing.T) {
 	}
 }
 
+func TestBindingPlateResolverUsesPrimaryKeyLookupWithoutSort(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("sqlmock.New() error = %v", err)
+	}
+	defer db.Close()
+	mock.ExpectQuery("SELECT plate FROM vehicle_identity_binding WHERE vin = \\? AND plate IS NOT NULL AND plate <> ''$").
+		WithArgs("VIN001").
+		WillReturnRows(sqlmock.NewRows([]string{"plate"}).AddRow("沪A12345"))
+
+	plate, err := NewBindingPlateResolver(db, "vehicle_identity_binding").PlateByVIN(context.Background(), " VIN001 ")
+	if err != nil {
+		t.Fatalf("PlateByVIN() error = %v", err)
+	}
+	if plate != "沪A12345" {
+		t.Fatalf("plate = %q", plate)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Fatalf("sql expectations: %v", err)
+	}
+}
+
 func TestSnapshotWriterCachesBindingPlateByVIN(t *testing.T) {
 	exec := &recordingSnapshotExec{}
 	resolver := &recordingPlateResolver{plate: "沪A12345"}