OBS: IMPORTANT INFO if your application is above 2GB in size!!
Yes! The bigger games you’ll find out there uses a CDN, usually side by side with GooglePAD.
GooglePAD is free to use, so if your game is 3GB, your most efficient and profitable solution is to use GooglePAD for 2GB and the last 1GB through your CDN.
Because CDNs cost scale with the project size.
This is a blog post on Google Play from a big company that saved a lot of money on CDN costs due to GooglePAD!
An example use cases of combining CDN and GooglePAD would be to use the extra 1GB from your own CDN in the areas of your application you rarely need/load for the user. That way you save money because not every user gets to that point in the game (Maybe the very latest area of the game that takes 10+ hours to reach) or that one Shop DLC that users can buy could be stored through your CDN.
GooglePAD PAKs should be used in as many common areas as possible simply because it’s free and efficient! 
Side note: It might not matter if the AAB file is above 2GB, when it goes through a Binary check on Google Play it will be split up into chunks with relevancy connections to one another, which means that the final download for your game may only be 1gb or even less.
The AAB contains ALL your files, all the texture compressions and so forth, which can make it bloat, and that’s totally fine and nothing to worry about.