resource management about online game

Hello everyone!
I have an online game project that needs dynamically load resources from AssetBundle to add new contents without update the client program.
For example, I have lots of high resolution sprites, and pack them into several bundles, and logically group them into a bundle so that I can load resources by name as if they are in a single AssetBundle.
But I can not load all AssetBundles at first and then load from them since it may take too much memory, and dynamically load a AssetBundle and extract resource is too slow.
So is there a strategy that can manage resources that can be dynamically add, fast loaded and take not too much memory? I see many really amazing online game made by Unity, and they all need high resolution resources and run fluently, is there a common solution for these problems?