MKTileOverlay from local tiles lags when zooming

Question

I have tiles stored locally on device and I'm loading them with the following code

override func url(forTilePath path: MKTileOverlayPath) -> URL {
    let tilePath = Bundle.main.url(
        forResource: "\(path.y)",
        withExtension: "png",
        subdirectory: "tiles/\(path.z)/\(path.x)",
        localization: nil)
    
    if let tile = tilePath {
        return tile
    } else {
        return Bundle.main.url(
            forResource: "empty",
            withExtension: "png",
            subdirectory: "tiles",
            localization: nil)!
    }
}

I create a MKTileOverlayRenderer in my viewModel

let overlay = TileOverlay()
    overlay.canReplaceMapContent = true
    overlay.minimumZ = 13
    overlay.maximumZ = 16
    tileRenderer = MKTileOverlayRenderer(tileOverlay: overlay)

And add that overlay in viewDidLoad of my ViewController to the mapView

mapView.addOverlay(viewModel.tileRenderer.overlay, level: .aboveLabels)

This calls my delegate method rendererFor overlay:

func mapView(_ mapView: MKMapView, rendererFor overlay: MKOverlay) -> MKOverlayRenderer {
    return viewModel.tileRenderer
}

I only have a small sample of tiles, 17MB, however there is a lag when zooming in and out and even sometimes on initial load of the overlay. I've even restricted the mapView boundary with MKMapView.CameraBoundary and zoom with MKMapView.CameraZoomRange.

How can I prevent this lag?

I'm using a Simulator: iPhone11, iOS 13.5