2nd RT: data (app server) and code (CDN) in parallel
Therefore you need two. But not all roundtrips are equal. A roundtrip to a CDN is much faster than a roundtrip to an application server and database, unless you have some funky edge database setup.
If you render on the server, your first roundtrip is slow because the client has to wait for the application server and database before it can show anything at all. If you render on the client then your first roundtrip is fast but the second one is slow.
