It’s correct that ng serve builds in memory.
Angular CLI does not have support for running a server and writing to disk at the same time.
If you are using your own server, etc., you can use ng build --watch, which will watch files just like ng serve, but will write them to disk, and will not run a server.
Check this official documentation on how to serve files from disk:
https://github.com/angular/angular-cli/wiki/stories-disk-serve