diff --git a/model/migrate_test.go b/model/migrate_test.go
index 62491bb5..2c2ec627 100644
--- a/model/migrate_test.go
+++ b/model/migrate_test.go
@@ -77,6 +77,17 @@ func TestFKSetNullOnDelete(t *testing.T) {
 	})
 }
 
+func TestCarBlockFKIndexes(t *testing.T) {
+	testutil.All(t, func(ctx context.Context, t *testing.T, db *gorm.DB) {
+		require.True(t, db.Migrator().HasIndex(&model.CarBlock{}, "CarID"),
+			"car_blocks.car_id must be indexed for FK cascade performance")
+		require.True(t, db.Migrator().HasIndex(&model.CarBlock{}, "FileID"),
+			"car_blocks.file_id must be indexed for FK cascade performance")
+		require.True(t, db.Migrator().HasIndex(&model.CarBlock{}, "CID"),
+			"car_blocks.cid must be indexed for gateway lookups")
+	})
+}
+
 func TestInferPieceTypes(t *testing.T) {
 	testutil.All(t, func(ctx context.Context, t *testing.T, db *gorm.DB) {
 		prep := model.Preparation{Name: "test", MaxSize: 1024, PieceSize: 1024}
diff --git a/model/preparation.go b/model/preparation.go
index 7a448435..fd19ab1a 100644
--- a/model/preparation.go
+++ b/model/preparation.go
@@ -304,7 +304,7 @@ type CarBlock struct {
 	// Associations - SET NULL for fast prep deletion, async cleanup
 	CarID  *CarID  `cbor:"-"                    gorm:"index"                                          json:"carId"`
 	Car    *Car    `cbor:"-"                    gorm:"foreignKey:CarID;constraint:OnDelete:SET NULL"  json:"car,omitempty"  swaggerignore:"true"`
-	FileID *FileID `cbor:"7,keyasint,omitempty" json:"fileId"`
+	FileID *FileID `cbor:"7,keyasint,omitempty" gorm:"index"                                         json:"fileId"`
 	File   *File   `cbor:"-"                    gorm:"foreignKey:FileID;constraint:OnDelete:SET NULL" json:"file,omitempty" swaggerignore:"true"`
 }