下载图像后，在自定义tableview单元格中重新加载约束或更新高度

I show 1 image in my cell and height need to be changed according to aspect ratio. But if I don't reload table, constraint is not changed and thus cell height too. If I use 'reloadData' or reload particular row, it is okay but scrolling performance is affected. One of the ways is to download all images first but might not be good I guess. How shall I do?I show 1 image in my cell and height need to be