I did some tests for the sample and it takes about 0.4s to load every zoom or pan. I think the differences on our PCs are caused by some reasons, such as the different “.sqlite” database, CPU, RAM, and so on.
There some options to improve the performance.
1.Apply the tile cache to overlay, like “layerOverlay.TileCache = xx”.
2.Change the tile size (TileHeight, TileWidth properties of Overlay) to bigger than default (256 * 256).
More information about tile cache please see here.