One way to drastically improve drawing performance for complex Konva shapes is to cache them as images. This can be achieved by using the cache() method to convert a node into an image object.
This particular tutorial of drawing 10 cached stars rather than drawing 10 individual stars sees about a 4x drawing performance boost. Caching can be applied to layers, groups, and shapes.
Note: The cache() method requires that the image is hosted on a web server with the same domain as the code executing it.