Is there a way to serve a specific node for certain paths? I'm using Pantheon and there doesn't seem to be a way to update nginx/apache config.

One of my templates is actually a single page app, and I'd like to tell Drupal to serve /node/1 for a couple of URIs. 

Get the current path alias or path? shows how I am able to get the current path in the .theme file.

Is there a way to serve a specific node for certain paths?
Core has URL aliasing built in, and having multiple aliases for a single path is supported.

You can manage these at /admin/config/search/path (assuming you have the core Path module enabled).