I've been using a lot of firebase lately and I'm looking into building a web app and hosting it on firebase as well. I know Firebase hosting lets you deploy html/css/javascript files, but is there any way to customize the server code to handle certain jobs on the server side? For example I'm concerned about putting my API keys (including firebase) on the client side since anyone can really see them. And I'm not too sure about encrypting things on the client side.
If this is not a feature currently, I hope Firebase introduces it soon! Maybe an option run Node/Express for their hosting. :)