Where does a web app execute?

Once a web app is deployed and it is being hosted, does it execute on the server or on the clients computer when accessed?

There is code that runs in both locations. Your Xojo code runs on the server, but our javascript framework code runs on the browser.

With that in mind, would it be true to say that the executable could be huge and bandwidth would not be an issue?

While it is true that the executable does not get downloaded, the framework may generate a lot of traffic back and forth to the server, as every user action you respond to has to be sent to the server, processed by your app, and then sent back to the user.

Keep in mind that the framework itself is ~200K, which is delivered once, and the event traffic is typically under 50K. The really big stuff (10,000 rows in a Listbox for example) usually begs for refactoring anyway.